Microbiology

 General term for very small organisms that

can not be seen with the naked eyes.



Importance: 1.Biotchnology 2.Pathology

 Main groups of micro-organisms

-viruses -Bacteria -Fungi -Protozoa -Algae

-Virology -Bacteriology -Mycology -Protozoology -Algology (Phycology)

Fungi Mould Yeast

Bacteria

Protozoa Viruses

Medical Bacteriology  The study of a group of

medically singlecelled Prokaryotic organisms called bacteria.

Antonie van Leeuvenhoek

1632-1723(1674 animacule)

Louis Pasteur (1822-1895)

Theory of germ disease Rabies vaccine Pasteurization

Robert Koch (1843-1910)

Anthrax bacillus 1877 Tuberculosis bacillus 1882 Vibrio cholera 1883

History  1875

- 1910 Description of many microbial diseases Evaluation and microscopic examination of microorganisms Cultivation of pathogen microbes Phenotypic characteristics of microorganisms

20th and 21th century  Electron microscope  Elaborated structure of microorganisms

such as bacteria, viruses, fungi etc.  Development of microbiology and its branches : Bacteriology ,Parasitology, Immunology, mycology, virology, algology, molecular biology etc.

Introduction of bacteria  Kingdom Protista  High Protistes (Protozoa, Fungi)  Simple Protistes (Prokaryotes)  Replication (Binary fission)

Doubling time every 20min

Procaryote cell

The structure of an eucaryotic cell

Impacts of microbes in the earth  Microbes found every where  Photosynthesis (algae )  Decomposition and recycling  Change of air nitrogen to nitrogen

containing compounds  Human and animal diseases  Fermentation and degradation

General structure of Bacterial cell  Difference

in size 0.1 -10µ

 Forms

cocci bacilli spirilium spirochaetes fusiform

Forms of bacteria

Forms of bacteria

General structure of a bacteria

Common structures bacteria cell Function

Chemical nature

Flagel

movement

protein

Pili

attachment, protection

protein

F or sex pili

transfer DNA under conjugation

protein

Capsule

attachment to surfaces, pro- polysaccharides tection against phagocytosis

Cell wall

protect, give form, stability

Cytoplasmic membrane

permeabilitets barriere, transport, energy, enzymes

Ribosomes

make synthesis of proteins

RNA, protein

Inclusions

Reservoir for nurishment

carbohydrate, lipid, protein, salts

peptidoglycan

Chromosomes genetic material

DNA

Plasmids

DNA

extrachromosomal DNA

Bacterial capsule  Capsule forms during active development

of bacterial cells (limited ,thick and sticky )  Loose soluble shield ( slime layer )  Capsule and slime layer formed : mostly from Polysaccharides some from Glycoprotein and rarely Protein

Bacterial capsule

Function and importance of capsule  Protection of bacteria against

Phagocytosis St. pneumonia  Antigenic chracteristics St. pneumonia  Binding to host’s organism St. mutans St. salivarus

The capsel of pneumococci made visible in Indian Ink preparation

Hyaluronic acid capsel of streptococus made visible by negativ staining

Mucoid colonies produced by abundant capsular production

Function and importance of capsule  Capsule formation is not

important in invitro live of microorganisms  Formation of capsule is related to existence of special substances like sucrose for St. mutans

Bacterial cell wall Cell wall is a protective structure for bacteria Unique form for bacteria  Saving from environmental dangers  Selective permeability  Keeping from biological and chemical substances  Entrance of nutrients  Defecation of metabolites  Seen in all types of bacteria except an Mycoplasma  

Gram positive cell wall  Peptidoglycan  Teichoic acid  Carbohydrates and proteins

 Peptidoglycan (murein)

NAG NAM Murein : form and size of bacteria protection against Osm.P

Teichoic acid  Polymer of either glycerol phosphat

+sugars + amine group containing sugars and amino acids  Different size and forms in different bacteria and even in strains of bacteria  Antigenic characteristics

Gram negative cell wall  Thin layer of murein  Outer membrane  Periplamic space (Proteins and

Oligosacchrides )  Cell membrane

 Outer membrane

like cell membrane structure Lipopolysaccharides +Proteins Inner layer of OM cotains proteins bind with murein layer Porin protein Penetration of molicules

G+ and G- cell wall

Peptido-glycan layer

Peptidoglycan monomer

Cell surface of Gram-positive, Gramnegative and acid-fast bacilli

Atypical cell walls  Lack of Gram positive of Gram negative

structure Mycobacteria and Nocardia  Some bacteria have no cell wall (Mycoplasma)  Structure of Mycobacteria cell wall : murien unique type of lipids such as Mycolic acid (a long chain fatty acid)

Mycoplasma

Atypical cell walls Fatty acids give a thick waxy nature to bacteria and:  are important for pathogenicity of Micobacteria.  Give a high degree of resistance to certain chemicals and dyes Resistance to chemicals is the basis for Acid fast stain

Atypical cell walls In some bacteria the walls are composed almost entirely form Polysaccharides and in some are pure protein.  Some bacteria lose cell wall during its life cycle called L- form or L-phase variants ( for the Lister Institute ) L- forms arise from a mutation in the wall forming genes or can be induced by treatment with a chemical like lysozyme or penicilline 

Atypical cell walls  When a gram positive cell is exposed to

chemicals loses the wall and becomes a Protoplast.  A gram negative if loses cell wall called spheroplast.

Protoplast and spheroplast forms of G positive and G negative bacteria

Bacterial cell membrane  Thin ( 5 – 10nm ) flexible sheet

molded completely around the cytoplasm  It is a bilayer coat containing : 30 – 40% of Phospholipids 60 – 70% of Proteins  Exceptions in Mycoplasma which contains high amounts of Sterols that stabilize and reinforce the membrane

Bacterial cell membrane  Cell membrane in some locations forms

internal pouches called mesosome  Mesosomes are promminent in G positives  Mesosomes increase the surface area available for membrane functions , participate in cell wall synthesis ,guide duplicated chromosomes into two chromosomes

Functions of cell membrane       

Energy reactions , nutrients processing and synthesis Regulation of tansport Selective permeability Discharge metabolic products into extracellular environment Most enzymes of respiration and ATP synthesis reside in cell membrane Synthesis of macromolicules for making envelope and cell appendages because of having enzymes Secretion of enzymes and toxins into extra cellular envinronment.

Protoplasm and internal contents  Dense gelatinous solution covered by

cytoplasmic membrane , a prominent site for biochemical and synthetic activities.  Contains 70 – 80% of water as solvent for the cell pool includes sugars, amino acids and salts.  Contains larger discrete cell masses such as chromatin body ,ribosome and granules

Bacterial chromosomes and plasmids  Chromosome :exists in the form of single

circular strand of DNA  Bacterial DNA is aggregated in a dense area of cell (nucloide).  Long molicule of DNA coiled around protein  Along its length genetic units that carry necessary information to bacterial maintenance, are located.

Plasmid  Unessential pieces of DNA  Resistance to antibiotics  Some toxins and enzymes  Genetic engineering

Ribosome ( site of protein synthesis) 

  

Tiny ,discrete spherical units called ribosome ( polysomes) Attached to cytoplasmic membrane A combination of rRNA 60% and Protein 40% Made from two subunits (Svedberg) 50s and 30s

Storage granules  Bacteria store nutrients during abandance

in different sizes and numbers like: glycogen granules, Polyphosphates and poly beta hydorxy butarate

Cell appendages  Flagella

and axial filaments  Pilli and fimbria 1 – Flagella ( bacterial propellers): motility device

Bacterial flagellum

1-7nm 20nm

Bacterial flagellum  All spirals  50% bacilli  Small number of

have flagella

cocci

Types of flagellated bacteria  Momotrichous :

lophotrichous

Amphotrichous

Peritrichous

Functions of bacterial flagella  Flagellated bacteria can move in response

to chemical signals (Chemotaxis )  Flagellum guides bacteria in environment

 The presence of motility is used for

identification of pathogens  Special staining methods and electron microscope needed to see bacterial flagella.  Cultivation of bacteria to a semisolid medium to know motility of bacteria  Hanging drop slide

Motility of bacterial cell

Axial filament (periplasmic flagella)  Seen in spirochetes which have a wriggly

locomotion  Made from a hook and filament  Coiled thread located in periplasmic space  A thin filament curls closely around the spirochetes and imparts a flexing motion to bacterial cell and contracts freely

Appendages for attachment and mating  Pili and fimbria (bacterial surface

appendages) provide adhesion and conjugation  Fimbria has an inherent tendency to stick to each other and to surfaces

fimbria

fimbria  Responsible for cells mutual clinging and

aggrgation  Making biofilms on rocks and glasses  Leading a surface in liquids  Colonization and adhesion to host cells and initiating infections e.g gonococci and E.coli

Pili (mating appendage)       

Pili : An elongate rigid tubular structure made of special protein ,pilin True pili only found in gram negatives Pili are involved in a mating process between cells called conjugation Transfer of DNA from one cell to another Production of pili controlled genetically Pili provide a cytoplasmic conection

Bacterial six pili

Bacterial endospore ( an extremely resistant stage)  Dormant bodies produced by gram

positive bacteria like genera Bacillus and Closteridia  Made when cell survival is threatened like starvation of nutrients or accumulation of toxic wastes  Spores are resistant to heat, radiation, chemicals and desiccation

Bacterial endospore  Mechanism of resistance is dehydration of

cytoplasm and production of special proteins that protects DNA  Heat resistanse of`endospore belongs to calcium dipicolinic acid  The exact role of heat resistance substances are unkonwn  There is little or no metabolism inside the spore

Endospore formation 1. forming a separate compartment for spore in mother cell  2. laying down various layers of spore  3. dehydration of spore  4. some spore forming bacteria are tractable allowing mutations during sporulation 

Bacterial endospore

The germination of endospore       

Spore forming bacteria revitalized when favorable condition arise In the presence of water, specific chemicals or environment stimulus Completion of process 1.5 h Germination agents are like amino acids,or an inorganic salts Agents stimulate formation of hydrolytic enzymes by spore membrane Enzymes digest the cortex and expose the core to water As the core rehydrates takes the nutrients and begins to grow

Medical significance of bacterial spore 

    

Some spore forming bacteria causes diseases like : Anthrax a skin and lung infection caused by: Bacillus anthracis Genus closteridium like Cl.tetani , Cl.perfringens ,Cl.botulinum Intruders of sterility because of their existence in soil and dust Contamination of culture media Harmful for wounds and burns Boiling (100 C) usually do not destroy spores

Methods used in Bacterial identification  Microscopic morphology

- Traits can be valuable in identification of bacteria: • Gram stain reaction • Acid fast reactions ( Ziehl Nelson ) • Structure including endospore, granules, capsules etc.

Methods used in Bacterial identification Macroscpic morphology : - Appearance of colonies including texture, size, shape, pigment, speed of growth and patterns of growth in broth and gelatin media  Physiological / Biochemical chracteristics; - biochemical tests are the mainstay for bacterial identification - Determining the presence of specific enzymes - sensitivity to antimicrobic drugs 

Methods used in Bacterial identification - Assessment of nutritional and metabolic activities e.g.; • fermentation of sugars • Capacity to digest or metabolize complex polymers such as proteins, polysaccharides, production of gas, presence of enzymes such as catalase, oxidase and decarboxylases • Special rapid identification test systems for major biochemical reactions

Methods used in Bacterial identification Chemical Analysis Analysis the types of specific structural substances such as chemical composition of peptides in the cell walls & lipids in membranes  Serological analysis: Surface and other molecules ( antigens) Antigen – antibody reactions Laboratory kits identifying bacteria in the specimen based on immunologic reactions 

Methods used in Bacterial identification  Genetic and Molecular analysis :

G + C base composition: The overall percentage of guanine and cytosine ( compared with A + T content ) in DNA is a general indicator of relatedness Bacteria with a significant difference in G+C percentage are genetically distinct species or genera like E.coli ( 48 – 52% G+C ) and P.aerogenosa ( 58 – 70% G +C )

Methods used in Bacterial identification DNA analysis using genetic probes: The exact order and arrangement of DNA code is unique to each organism . By Hybridization technique bacterial species are identified by analyzing segments of its DNA This technique requires small fragments of specific single stranded DNA or RNA

Methods used in Bacterial identification rRNA analysis : Sequence of nitrogen bases in r RNA Major difference in the sequence of RNA Useful for differentiating major groups like super kingdom Used for differentiating species level ( Mycobacterium and Legionella )

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Survey of Pathogen procaryotes Bacteria

Eubacteria

Archaebacteria

Bacteria

Typical bacteria

Cocci , bacilli , spirals Binary fission

Atypical bacteria

Mycoplasma Cell wall deficiant Bacteria Pleomorphic High level sterol in CM

Chlamydia Smaller then rickettsia O,Int. parasites

Rickettsia Small g negative Obligate intracellular parasites

Microbial Nutrition  Nutrition is a process which nutrients

(chemical substances ) are aquired from the environment and used in cellular activities such as metabolism and growth  Living things require sources of elements such as C, H, O, P, K, N, S,Fe, Na, Cl , Mg

Microbial Nutrition  Any substance that must be provided to

organism is called Essential Nutrient Macronutrients: Carbohydrates, Proteins, and C and H containing substances Micronutrients ( Trace elements ) Mn, Zn and Ni: much smaller amounts involved in Enzyme function and maintenance of protein structure

Microbial Nutrition Growth Factors An organic compound such as amino acid, Nitrogen base and Vitamin that can not be synthesized by an organism and must be provided as a nutrient is a growth factor Essential amino acids Haemophilus influenza (meningitis and RTI) can grow only when Hemin (factor X ) NAD ( factor V) Thiamin and Pantothenic acid Uracil, Cysteine

Environmental Factors That Influence Microbes  Temperature (Heat, cold) Gases , acid ,

radiation , Osmotic and Hydorostatic pressures and other microbes

Temperature adaptations Range of Temperature : • Minimum temperature • Maximum temperature • Optimum temperature Microorganisms are in Three ecological groups : • Psychrophile ( 0 – 15 C ) true psychrophile Facultative psychrophile • Mesophile ( 20 – 40 C ) • Thermophile (45 – 80 C ) mostly spore forming and rarly pathogens 

Gas requirements   • • •

Atmospheric gases that most influence microbial growth are Oxygen and Carbon dioxide According to use of gases microbes of Three groups use oxygen and can detoxify Those that can neither use oxygen nor detoxify Those that do not use oxygen but can detoxify

 How microbes process oxygen  When oxygen enters a cell transrformed

into several toxic products like O, peroxide and superoxide iones

Gas requirements  Aerobic organism  Facultative anaerobe  Microaerophile  Anaerobe

 Effects of PH  Osmotic Pressure

Microbial growth  A cell synthesizes components of new cell  The number of cells increases  Binary ,transverse fission

cell elongation septum formation septum completion cell separation

Bacterial cell division  Generation time (doubling time )

- mother cell 1 - first generation 2 - second generation 4 - third generation 8 - 4th 16 -…

growth rate different in species of microbes most Pathogens 20 – 30 min e.g. S.aureus , S.enteritidis  Minimum generation time 5 – 10 min  Max -------------------- 10days – weeks 

Microbial growth Stages in the Normal growth curve  Lag phase  Exponential growth ( log ) phase (

maximum rater of cell division )  Stationary growth phase  Death phase ( limiting factors )

The growth curve in bacterial culture

Microbial metabolism Definitions

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

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Metabolism: The processes of catabolism and anabolism Catabolism: The processes by which a living organism obtains its energy and raw materials from nutrients Anabolism: The processes by which energy and raw materials are used to build macromolecules and cellular structures (biosynthesis)

Infection & Disease  Relationship between microbe and host :

mutualism commensalism Parasitism  Microbes live in human body as: Colonists ( normal flora ) Transient Pathogen

Normal flora  Normal flora are bacteria, fungi, and

protozoa that live on or within the bodies of animals and plants. Normal flora, by definition, do not cause disease in healthy individuals. Instead, they are commensalists or mutualists with regard to the host. That is, in addition to basically not harming the host, they can even do some good.

•

Normal flora are found mostly:        

on the skin in the eyes in the nose in the mouth in the upper throat in the lower urethra in the lower intestine especially in the large intestine

Microbial antagonism [microbial competition]

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Colonization inhibition:

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•

•

A process by which pathogenic microorganisms are inhibited by normal flora from colonizing healthy organisms. Mechanisms by which this inhibition occurs includes:  competing with pathogenic microorganisms for nutrients  competing with pathogenic microorganisms for space  producing toxins that are harmful to some pathogenic microorganisms

Normal flora are symbionts

 

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Normal flora tend to be commensal or mutual symbionts adapted to the special conditions found in various body locations. Transient microbes Transient microbes are members of the normal flora that are not always present or are present for only a few days, weeks, or months before disappearing

Normal flora  Normal flora differs in individuals in quality

and quantity  In normal conditions some internal organs and systems like Pancreas, spleen, liver, gall bladder, urinary bladder, Nervous system and blood are sterile  New born fetus is sterile

Flora of the human skin      

Waxy cuticle nature of skin permits microbes Flora resides on dead external layer of skin Flora does not extend into dermis and subcutaneous levels Oily, moist skin supports more prolific flora Humidity occupational exposure and clothing also influence its character Transition zones of skin where it joins with mucous membranes harbor a rich flora

Flora of the human skin  Two cutaneous populations

- transient population - resident population ( lives & multiplies in deeper layers of the epidermis and in glands and follicle bacteria (Staphylococci, Corynobacterium and Propionibacterium ) and yeast

Indigenous flora of specific regions

Flora of Gastrointestinal tract  Receives food and removes wastes  Flora of the mouth :

most common residents are aerobic Streptococcus sanguis, S.salivarius, S.mitis ( S.mutans and S.sanguis make dental caries by forming sticky dextran slime layer from simple sugars

Flora of large intestine  Huge population of microbes (108 – 1011

per gram feces)  10 – 30% of fecal volume anaerobic bacteria ( bacteroides, Bifidobacterium, Fusobacterium, & Closteridium) Coliforms ( E.coli, Enterobacter, Citrobacter)

Flora of respiratory tract  Streptococci (nasal passage & pharynx)  Nasal entrance ( S.aureus )  Mucous membrane of nasopharynx

( Neisseria species )  Bronchi and lungs are unfavorable habitats for permanent residents

Flora of Genitourinary tract  Vagina and outer opening of the urethra in

female  Anterior urethra in males  Residents of urethra ( nonhemolytic streptococci, staphylococci, corynobacteria, and occasionally coliforms  Vagina ( lactobacilli)  (diphteroides, Staphylococci, streptococci and some coliforms )

Human normal flora habitates

Importance, benefits and defects of Normal flora  Microbial antagonism  Colonization and inhibition  Producing anti bacterial substances  Improvement of Immunity system  Synthesis of important substances

Problems in presence and absence of Normal flora 

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



Transition to an abnormal region e.g. entrance of S.epidermidis with catheterization (endocarditis ) Existence of Potential pathogens instead of normal flora by using Antibiotics Cl.dificile and colitis Transformation of harmless food to carcinogenic derivatives by flora ( sweetner cyclamate to cyclohexamine by sulfactase Development of flora in immunocompromised individuals

Development of infection  Attachment of pathogens and hosts  Pathogenicity and  Host condition Pathogen Microorganisms

True pathogens

Opportunistic Pathogens

True pathogens  Pathogens which produce infections and

cause disease in healthy people with complete immunity system Plague (Yersinia) ,influenza , Rabies virus,malaria

Opportunistic Pathogens  Immunodeficiency  Abnormal region

Factors important for getting infections            

Infancy,prmaturity Malnutrition Genetic defects in immunity Acquired immune deficiency syndrome (AIDS) Physical and mental stress Organ transplant Cancer Chemotherapy/Immunosuppressive drugs Anatomical defects Diabetes Liver disease Surgery

Portal of infections entrance  Exogenous

source  Endogenous source  Infectious dose (inoculum size )

Mechanisms of invasion and establishment of the Pathogens  Fallowing entry of Pathogen, next stage in    

infection requires : Binding to the host Penetration of barriers Establishment in the tissues Achievement of pathogens depends upon its biochemical and structural chracteristics

Mechanisms of invasion and establishment of the Pathogens  Adhesion : A process by which microbes

gain a more stable foothold at the portal of entry.  Bacterial pathogens mostly attach by: fimbriae(pili) , flagella ,Adhesive slimes or capsules  Viruses attach by specialized receptors  Protozoa can infiltrate by locomotion of organelles

Mechanisms of adhesion by Pathogens

Virulence factors  Exoenzymes  Toxins  Antiphagocytic factors  Many substances called toxins function as

enzyme

Exoenzymes  Extracellular enzymes:

Secreted by many bacteria, fungi, protozoa and worms Break down & inflict damage on tissues Enzymes dissolve host defense barriers Mucinase : digests protective coating on mucous membranes & is a factor of amebic dysentery

Keratinase : principle components of skin and hair secreted by fungi and causes ringworm Collagenase :Principle fiber of connective tissue an invasive factor of Clostridia Hyaluronidase ; hyaluronic acid which cements animal tissues staphylococci, streptococci, clostridia & pneumococci

Extracellular enzymes  Some enzymes react with blood

components coagulase produced by Staphylococci, clotting of blood plasma  kinases (Staphylokinase, Streptokinase): dissolving of fibrin clots  Streptase ( kind of streptokinase) for therapy of thrombi

Bacterial toxins  Potent source of cellular damage  Toxin: Specific chemical product of

microbes, animals and plants that is poisonous to other organisms  Toxigenicity* is a genetically controlled characteristic and is responsible of Toxinoses  Toxemia: toxin is spread by blood from site of infection (Tetanus and Diphtheria )  Intoxication: ingestion of Toxins (botulism)

Classification of Toxins  Toxins named according to target :    

Neurotoxin Enterotoxin Hemotoxin Nephrotoxin

Tradition classification of toxins  According to their origins:

Exotoxin : an unbound toxin molecule secreted by a living bacterial cell into the infected tissue called Exotoxin  Strong specificity to target cell  Dangerous and deadly  Affect cell by damaging cell membrane 

 Hemolysin :CM of RBC & release Hb  When cultivate on Blood Agar colonies are

different - Streptolysins of St.pyogenes - alpha and beta toxins of S.aureus - Pattern of hemolysis identify bacteria and degree of Pathogeniciy

 Toxin of Cl.tetani blocks the action of

spinal neurons  Toxin of Cl.botulinum Prevents transmission of nerve-muscle stimuli  Pertusis toxin inactivates the respiratory cilia  Cholera toxin provokes profuse salt and water loss from intestinal cell

 Endotoxine: released after lyses of cell  Lipopolysaccharides part of OM of gram

negative  Systemic effects on tissues and organs  Depending to present amount of Endotoxin it causes fever, inflammation, hemorrhage and diarrhea  Blood infections with G negatives like Salmonella, Shigella, Niesseria meningitidisAnd E.coli are dangerous

Antiphgocytic factors  Phagocytes :specific type of WBC which

engulf and destroy pathogen bacteriaby enzymes and other antibacterial chemicals  Killing Phagocytes by specific substances  Leukocidins of of Staphylococci and Streptococci are toxic to WBC

 Some Microorganisms secret slime layer

and capsules that make them Physically resistant to phagocytosis St. pneumoniae, Sal.typhi, Neisseria meningitidis & cyptococcus neoformans  Some bacteria are adapted to survival inside Phagocytes after ingestion Legionella, Mycobacterium, rickettsia

Establishment, Spread and Pathologic Effects       

Aided with virulence factors microbes settle and cause damage to target organ Type and scope of injuries Adverse effects of enzymes, toxins and other factors Weaken host tissue Obstruct tubular structures blood vessels, lymphatic channels, fallopian tubes and bile duct Cause death cell and tissue death (necrosis) Viruses destroy cells by multiplying in and lysing them

Patterns of Infection  Localized infection (boil, warts, fungal skin

infection)  Systemic infection: spread from initial site to other tissues  Viral : measles, rubella, and chicken pox )  Bacterial : brucellosis, typhoid fever … Rabies :from bite wound along nerve tract to brain

 Focal infection : TB  Toxemia (local infection and general

effect), tetanus  Mixed infection: several agents simultaneously (synergetic infections)  Cooperate in breaking down a tissue  Gas gangrene, dental caries are mixed infections

 Primary infection  Secondary infection (chicken pox, primary

infection) with S. aureus  Acute infection ,rapid ,sever, short lived  Chronic : progress & persist for long time  Sub acute infection

Signs and symptoms  Pathologic changes causes signs and

symptoms  Signs ( noted by observers )  Subjective evidence sensed by patients  Complex of signs and symptoms called Syndrome

s

Human immunity system  Immunology: study of biological, chemical

and physical events surrounding the function of immune system  Immunity : from immune Gr. Free, a state of resistance to infection

Defense Mechanisms of the Host in Perspective  The host defending itself against

microorganisms  Existence of remarkable complex defense system Defense system

Innate nonspecific Immunity

Specific immunity

Defense Mechanisms of the Host in Perspective  First line of defense  Second line of defense  Third line of defense

First line of defense  Barriers which block invasion at the portal

of entry  Limits access to internal tissues of the body  Non specific  Does not involve recognition of specific foreign substances

Barriers at the Portal of entry  Anatomical parts of the body (Physical)  Chemical barriers  Genetic barriers

Physical (anatomical) barriers       

Skin and Mucous membrane (RT & GIT) built in defenses Skin :Stratum corneum has compacted cells impregnated with Keratin( insoluble protein ) Mucous membrane: blinking and lacrimation of eyes (tears ) Flow of saliva (carry microbes to stomach) Vomiting and defecation (evacuation ) Sweat glands Nasal hair traps larger particles

Physical (anatomical) barriers  Nasal hair traps larger particles  Rhinitis in cold and allergy  In trachea & bronchi ciliated epithelium

(ciliary escalator) removes substances to Pharynx  Sneezing and coughing

Physical (anatomical) barriers  Genitourinary tract  Urination  Presence of Normal flora of GUT

Non specific chemical defenses       

Sebaceous secretion Meibomian glands (secret an anti microbial substance and lubricates conjunctiva Lysozyme :hydrolyses Peptidoglycan Sweat; High lactic acid and electrolyte concentration Acidic PH of skin Intestine’s digestive juices Acidic PH of vagina

Genetic defenses  Some hosts are genetically immune to

disease of other host  Some viral infections  Humans have gene of sickle cell anemia are resistant to malaria  Susceptibility to TB, leprosy and systemic fungal infections

Second line of defense  Internalized system of protective cells and

fluids include inflammation and phagocytosis  Acts rapidly local and systemic

Third line of defense  Acquired  Highly specific  Lymphocytes  Reaction with each microbe unique

protection  Long term immunity

Systems involved in immune defenses   1. 2. 3. 4.

Immune system does not exist in a single, well defined site. Long complex network of cells and fluids Reticular Endothelial system Extra Cellular Fluid Blood Circulation Lymphatic system

Immune function of the Reticular Endothelial System  A network of connective tissue fibers  Interconnects nearby cells  Mashes with massive Connective tissue

network surrounding all organs  Provides passageway within and between tissues and organs  Helps phagocytic cells  Endowed with macrophages waiting attack of intruders

Circulation System  Blood ; liquid connective tissue consisting

of blood cells and Plasma  RBC , WBC , Platelet  Granulocyte (Polymorphonuclear L)  granulocyte ( Mononuclear L)

Granulocytes  Neutrophile 55 – 90% of WBC  Phagocytosis  Cytoplasmic granules 

digestive enzymes

Granulocytes  Eosinophile  1 – 3% of WBC  Exact role is unknown  Granules ( peroxidase, lysozymes and

digestive enzymes )  Weak phagocytic activity  Increases in parasitic diseases

Basophile  0.5% of WBC  Increase Allergy and Inflammation  Granules ( histamine, serotonin , heparin

Agranulocyte

Agrnulocyte Monocyte

lymphocytes B cells

T cells

Lymphocyte  20 – 35% of total WBC  B cells ( bone marrow , bursa of fabricius)  T cells ( thymus gland)  Important part of third line defense 

B Cells & T cells  Reacts with antigens  Humoral immunity  Activates and produces plasma cell  T cells

• Cell – mediated immunity

Monocyte  3 – 7 % of WBC  Largest cells of WBC  Changes to macrophages in tissues  Phagocytosis  Processes foreign molecules

and

presenting to lymphocyte  Secrets active compounds that assist, mediate, attract and inhibits immune cells and reactions

Non Specific Immune Reactions of the body’s compartments  Mechanisms play role in host defense

1.inflamation 2. Phagocytosis 3. Interferon 4.Complement

What is inflammation ?  Inflammation is a process in which the

body’s white blood cells and chemicals can protect us from infection and foreign substances such as bacteria and viruses.

inflammation 

      

Inflammation is a sequential protective response to injury that stimulates the influx of beneficial cells and chemicals that can protect against infection and further damage at the site . A reaction to any traumatic event in the tissues Infective Non infective Rubor (redness) calor (warmth ) Tumor (swelling) Dolor ( pain)

What diseases are associated with inflammation  Rheumatoid arthritis  Shoulder tendinitis or bursitis  Gouty arthritis  Polymyalgia rheumatica

Can inflammation affect internal organs?    

Inflammation of the heart (myocarditis) may cause shortness of breath or leg swelling Inflammation of the small tubes that transport air to the lungs may cause an asthma attack Inflammation of the kidneys (nephritis) may cause high blood pressure or kidney failure Inflammation of the large intestine (colitis) may cause cramps and diarrhea

The stages of inflammation  Vascular changes: early inflammatory

events  Controlled by: Nervous stimulation, chemical mediators and cytokines  Vasoactive mediators (Chemotactic factors )  Mediators of inflammation cause fever, stimulate lymphocytes and prevent viruses spread

The stages of inflammation  Edema ( leakage of vascular fluid to

Tissues  Caused by vasoactive* substances  Blood borne components to extracellular spaces  Local swelling and hardness (EDEMA)  Sometimes accumulated Phagocytes contribute to pus (Streptococci, Staphylococci, & other pyogenic bacteria

Inflammation  Mobilize & attract immune components at

the site of injury  Set in motion mechanisms to repair tissues and clear away harmful substances  Destroy microbes and block further invasion

Fever (adjunct to inflammation)

Fever (adjunct to inflammation)  Hypothalamus thermostat

37C

 Initiates by pyrogen  Universal symptom of infection  Allergies, cancers, etc.  FUO  Low grade fever : 37.7 -

38.3C  Moderate fever : 38.8 - 39.4C  High grade fever : 40 - 41.1C

Fever  Pyrogens : pyr: fire ,gennan :produce

- Exogenous: Product of infectious agents - Endogenous: Product of Monocytes, neutrophils & macrophages during Phagocytosis and are parts of immune response

Benefits of fever  Inhibits multiplication of temp-sensitive MO

such as polio Virus, cold V, Herpis zoster, Mycobacteria and Siphilis spirochete  Impedes nutrition of bacteria reducing availability of Iron Macrphages stop iron releasing for bacterial enzymatic reactions  Increases metabolism & stimulates immune reactions and protective physiological Process like hematopoises,

Phagocytosis  Process of ingestion and destroying of

foreign materials by Phagocytes  General activities of Phagocytes:  Survey tissue compartments and discover microbes, particulate matters & dead cells  Ingest and eliminate materials  Extract antigens from foreign matters

Main types of Phagocytes 

Neutrophile



Monocytes



Macrphages

Stages of Phagocytosis  Chemotaxis, and ingestion;

Phagocytes migrate to region of inflammation by stimulation of invaders or host cells - Accompanied with opsonization - Phagocytes extend pseudopodes after contact with prey - Inclose cells in Phagosomes -

Phagolysosome formation and killing Lysozyme fuse with Phagosome

Destruction & Elimination systems  Oxygen dependent system ;

Myeloperoxidase; Forms hallogen ions OCl- Hydrgen peroxide - Super oxide anion  liberation of lactic acid, lysozyme, NO  Proteolytic and hydrolytic enzymes

Stages of Phagocytosis

interferon  Small proteins produced by certain WBC &

tissue cells that is used in therapy of viral infections and cancer  Alpha int. ( lymphocytes & macrophages )  Beta int.( fibroblasts & epithelial cells)  Gamma int. (T – cells)  Against: viruses; RNA, immune products & Antigens

interferon  Bind to cell surface & induce change to

expression  Anti cancer effects  Tumor suppressor effects  Alpha & beta stimulate Phagocytes  Gamma IFN is an immune regulator of macrophages, B & T cells

Characteristics of Antiviral Interferon       

Binding virus to receptor sends signal to cell nucleus to activate genes coding for interferon Interferon secrets to extracellular Enters uninfected cells IFN activates a gene for a protein Protein interferes multiplication of virus It is not virus – specific Valuable in treatment of viral infections

Inhibition of virus multiplication by interferon

Other roles of interferon  Immune regulatory cytokines  Alpha IFN (T Cells) activates NK

(cytotoxic T)  Beta IFN maturation of T & B cells  Gamma IFN inhibits cancer cells, stimulates B cells activate macrophages  Enhances effectiveness of Phagocytosis

Complement  Complex multi-duty system ( C factors )  Completing immune reactions  20 blood proteins work in concert to

destroy invaders  Sources of complement factors : hepatocytes, lymphocytes, monocytes

Specific immunities The Third Line of Defense  When barriers & non-specific defenses fail

to control infection  Resistance developed after ailments Measles  Long term immunity

Acquired specific immunity  Elegant and

complex matrix of interrelationships between lymphocytes & macrophages  Long term protection  Specificity & memory (selective activities)  Chicken pox measles etc.

Principle stages of ASI 1. 2. 3. 4. 5.

Lymphocyte development & differentiation The processing of antigens Challenge of B & T cells by Antigens B lymphocytes and production and activities of Ab T lymphocyte responses

Stage1 development of lymphocytes  Stem cells

B and T lymphocytes  Lymphocyte originate in hemopoitic tissue  B antibody  T cytokines and initiate & coordinate entire immune response

Stage 2 Processing of Antigens  Invaders swept up with blood, lymphatics

and RES  Macrphages ingest and present antibody to lymphocytes  Presentation : Antigen in surface of macrophages + MHC II  Ag+MHC recoginsed by T helper cells  T cells produce Cytokines proliferate and activate B cells

Stage 2 Processing of Antigens  B cells produce plasmsa cells and it

produces Immunoglobulines

Stage 3 Activation of lymphocytes and clonal expansion  Lymphocytes proliferate Produce clones of

progeny include groups of responder and memory cells

Stage 4 Activation of B lymphocytes  B cells produce plasma cell

plasma cell

secretes Ab  Secreted Ab circulate in tissue fluid lymph and blood  The antigen binds with antibody  The Ag is marked for destruction Opsonization& neutralization

Stage 5 T lymphocytes response  Differentiate

to one of four subtypes :  Cell mediated immunity Helper T cells  Suppressor T cells  Delayed hypersensitivity T cells  Cytotoxic or killer T cells

Functions of T cells

Markers on Cell surfaces Receptors confer specifity & identity Glycoproteins in cell surface (glycoproteins + additional carbohydrate fragments During maturation Mac. And Lym’s certain genes code for cell receptors  To perceive & attach to nonself (antigens)  To promote recognition of molecules  To receive & transmit chemical messages among other cells  To aid the cellular development

Major Histocompatibility Complex  One set of genes that codes for human

cell receptors isMHC  Gives rise glycoproteins called MHC antigens (HLA)  Genes code for MHC located on 6th chromosome

MHC Groups  MHC I

Protein found on all nucleated cells  MHC I recognize self molecules  MHC II on Mac, B cells & Ag Presenting Cells  MHC II code for immune regulatory receptors and react with foreign Ags  MHC III codes for certain complements C2 & C4

The clonal selection theory and lymphocyte development  Lymphocytes use 500 genes for receptors  There are millions of antigens  Different lymph receptor to each unique

Ag  Undifferentiated lymphocytes undergo genetic mutations & recombinations while they proliferate. This process leads to extreme variation in the expression of their receptor specificity

Tolerance to self  Any lymphocyte mount a harmful response

against self molecules is eliminated (tolerance to self )  In some auto immune diseases immune system loses this tolerance

The specific B-Cell receptors  In B cells genes of immunoglobulin

proteins exist  Ig :large glycoprotein molecules serve as specific receptor of B cells and antibodies  Ig is composite of four polypeptide chains  A pair of heavy (H) chains  A pair of light (L) chains  Symmetrical Y shaped

Basic structure of immunoglobulin

Antigen binding site  Antigen binding site; formed by H & L

chains  Highly variable in shape to fit antigens  Versatility is because of variable regions ( amino acid composition is varied )

T cell receptors  Protein  Formed by genetic modification  Having variable and constant regions  Smaller and does not appear humoral

functions

Characteristics of Antigens      

Ag : is a substance provokes an immune response in specific lymphocytes Being perceived as a foreign substance Not a constituent of the body Whole microbes and their parts Cell or substances from human, animals, plants & various molecules Molecule of complex compositions proteins and protein containing compounds

Antigens  Proteins and polypeptides( enzymes,

albumin, antibodies, hormones, exotoxins)  Lipoproteins ( cell membranes)  Glycoproteins ( blood cell markers)  Nucleoproteins ( DNA complexed to proteins, but not pure DNA)  Polysaccharides ( certain bacterial capsules) and lipopolysaccharides

Antigen characteristics  Large enough for immune attention

>1000MW are seldom complete Ag  1000 – 10000MW weak Ag  100000 and more strong Ag  No large size is only sufficient for antigenicity e.g. glucose 

 Antigen diterminant : active site  Primary signal that molecule is foreign  Tertiary shape of determinant is key for

lymphocytes receptors  Many foreign complex molecules have strong antigenicity  Numerous determinant  Mosaic antigens

 Small molecules consist only a

determinant can’t elicit immune response called haptens  Drugs and innocuous environmental chemicals

Special types of Ag  Auto antigens : molecules escape from

self tolerance  Auto immune disease Rheumatoid arthritis  Allo antigens :cell surface markers ( blood groups )  Allergens : Ag evoke allergic reactions

Antigen-Antibody interactions  Ag binding site To Ag is similar to Enzyme

substrate  Opsonization : stimulated by opsonins  A process which microorganisms or the particles coated with specific Ab and more readily recoginized by phagocytes

Complement fixation :Ab + complement------- rupturing of cells and viruses  Neutralization : Abs fill the surface receptors on a virus or the active site of a molecule to prevent it from functioning normally Anti toxins : neutralize bacterial exotoxins 

Function of crystalizable fragment  Fab

binding to antigen  Fc : can bind to certain receptors of cell membrane ( moncyte, mast cell, basophile lymphocyte )  Effect : depends upon cell’s role

 Opsonization  Certain Ab have receptors on Fc for fixing

complement  In some cases binding of Fc causes cytokine release (IgE binds to basophile which causes release of allergic mediators)  Size and amino acid comp of Fc determine Ab permeability

The classes of Immunoglobulin  IgG : monomer, by memory cells  Neutralization  Opsonization  Complement fixation  Capable of crossing placenta

 IgA:

1 - monomer (small amount in blood ) 2 – dimer : significant component of mucous and serous secretions of salivary Gland, intestine , nasal membrane ,breast GUT and lung  Formed in plasma cells Attached by J chains

 IgM;

pentamer attached by J chain  Plasma cell  Large molecule  Comp fixation  Opsonization

 IgD : small amount  Serve as receptor for Ag on B cells  Triggering molecules for B cell activation  Immune supression

 IgE :  Allergic reactions  Fc binds to mast cells and basophile  Stimulate inflalmmatory response  Mediators : anaphylaxis , asthma ,

allergies

Classifying specific immunity  Active  Passive  Natural  Artificial immunity