1Immunity 1 2010.IMDCppt

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Dr Shamim Mumtaz Prof of Microbiology The way in which the body protect itself from invasion by pathogenic microorganisms and provide a defense against their harmful effects.

Learning objectives : 

Learning objectives Define immunity antibody, epitope, hapten and cluster differentiation markers. Differentiate between innate and acquired immunity Enumerate the components of innate and acquired immunity Functions of innate and acquired immunity Process Of Specific Immune Response Differentiate active and passive immunity. Define antigen, enlist its types. Mechanism of humoral and cell mediated immunity. Define Cytokines, tabulates its types ,sources and functions.

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Downloaded from: Robbins & Cotran Pathologic Basis of Disease (on 4 October 2005 05:17 AM) © 2005 Elsevier

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LINE OF DEFENCE AGAINST MICROBES

Innate arm of immune system : 

Innate arm of immune system Provided by all the mechanisms that form an immediate non- specific barrier to infection. 1. Physical barriers to infectious agents : (Intact skin, mucosa) 2. Phagocytic cells; ( neutrophils, macrophages, natural killer cells) 3. Certain proteins like complement ,interferons, lysozymes, acute phase response proteins 4. Processes;--- Phagocytosis, inflammation 5. Commensal flora

Innate Immunity--- Natural Barriers : 

Innate Immunity--- Natural Barriers

Functions of innate immunity : 

Functions of innate immunity 1.Kill the invading microbes 2.Activate the acquired (adaptive) immune responses . Although successful in eliminating microbes & preventing infectious diseases . But in the long run not sufficient for human survival. e.g ---children with severe combined immunodeficiency disease( SCID) who have intact innate immunity but not acquired ,suffer from repeated ,life threatening infections.

Functions of acquired immunity : 

Functions of acquired immunity 1.Inhibits organisms like fungi ,parasites & certain intracellular bacteria 2. kill virus infected cells 3. Kill tumor cells 4. Neutralize toxins and viruses, 5. Opsonize bacteria (Phagocytosis) Through its Cell Mediated (T cells) and Antibody Mediated immune components

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Process Of Specific Immune Response Class 11 MHC Antigen PRESENTATION BY APCs RECOGNITION of foreign organisms by specific immune cells 3.ACTIVATION OF SPECIFIC IMMUNE CELLS 4.RESPONSE;---that specifically targets the organisms for destruction.

1. ANTIGEN PRESENTATION by APCs in the presence (Macrophages, dendritic) or absence of MHC 11 ( B cells ). : 

1. ANTIGEN PRESENTATION by APCs in the presence (Macrophages, dendritic) or absence of MHC 11 ( B cells ).

Recognition of foreign antigens through “pattern-recognition receptors” {e.g ;Toll –like receptors ( TLR 4) } : 

Recognition of foreign antigens through “pattern-recognition receptors” {e.g ;Toll –like receptors ( TLR 4) } TLR 4 are present on the surface of macrophages, They recognize molecular pattern present on the surface of many microbes ( not present on human cells) & transmits signals to cellular nucleus , inducing the production of cytokines and TNF.

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Process Of Specific Immune Response RECOGNITION 2. ACTIVATION OF IMMUNE CELLS to produce Ab 3. RESPONSE

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How it all works together

Types of Acquired (Adaptive Immunity) 1. Active Immunity : 

Types of Acquired (Adaptive Immunity) 1. Active Immunity The host actively produces an immune response through producing 1. Antibodies 2. Activated T cells (helper & cytotoxic ) After contact with foreign Ag through ;--- 1. infection (Clinical or sub clinical ) 2. immunization-- vaccination (with live or killed infectious agents or their Ags ) or 3. Exposure to microbial products (toxins, toxoids)

Types of Acquired ( Specific ) Immunity 2. Passive Immunity : 

Types of Acquired ( Specific ) Immunity 2. Passive Immunity Resistance based on the introduction of preformed Abs (or antitoxins) from another host 1.Administration of antitoxins (against diphtheria, tetanus, botulism) to neutralize toxins produced by these organisms. 2.Preformed Ab against certain viruses (Rabies ,Hepatitis B) can be injected during the incubation period to limit viral replication. IgG from mother to fetus during pregnancy IgA from mother to newborn during breast feeding

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Characteristics of Active & passive immunity

Passive -active Immunity : 

Passive -active Immunity Immunity involves giving both ;--- preformed antibodies (immune globulins) ( to provide immediate protection) and a vaccine (to provide long term protection) . Given at different sites to prevent the antibodies from neutralizing the immunogens in the vaccine. e.g ;---Tetanus, rabies, hepatitis

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Antigens:--- Are molecules that react with antibodies . Molecular Size>10.000 Immunogens;--- are the molecules that induce an immune response . In most cases the terms are used interchangeably .

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Types of Antigens 1.Extrinsic antigens; micro-organisms, transplanted organs, ingested/inhaled/injected materials. 2. Intrinsic antigens : Altered self antigens Partial denaturation due to some disease process Transformation in tumor 3. Sequestered antigens ; Colloid or eye lens proteins if accidentally exposed to immune system, excite an immune response .

Features of molecules that determine their Immunogenicity : 

Features of molecules that determine their Immunogenicity 1. Foreignness (Non self) 2. Molecular Size ; >100,000 potent immunogens < 10,000 weakly immunogenic 3. Chemical Structural complexity; heteropolymers ------more immunogenic homopolymers------- less immunogenic

Immunogenicity : 

Immunogenicity Antigenic Determinants (Epitopes) Exact part of the antigen against which an immune response is generated . Epitopes are made up of 4-8 AA or sugar residues. Most Ags are multivalent . Dosage, Route and Timing of Ag administration also effect immunogenicity.

Immunogenicity : 

Immunogenicity 6. Adjuvants They are chemically unrelated to the antigens but enhance the immune response by non-specifically stimulating the immune reactive cells or by releasing the immunogen slowly. e.g. some human vaccines contain adjuvants like aluminium hydroxide or lipids . 7. Age & immune response Immunity less optimal at both EXTREMES of life .

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Haptens A molecule that is not immunogenic by itself but can react with specific antibody after combining with some intrinsic proteins (carrier).e .g lipids, carbohydrates, nucleic acids, poison ivy and drugs like penicillin etc . CD markers (Cluster Differentiation markers) Cell surface molecules of leukocytes and platelets that are distinguishable with monoclonal antibodies and may be used to differentiate different cell populations e.g CD3, CD4+,CD8+Tcells markers

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Clone A family of cells or organisms having a genetically identical constitution. Cytotoxic Having ability to kill cells Leukotrienes A collection of metabolites of arachidonic acid which have powerful pharmacological effects

Cytokines : 

Cytokines Soluble mediators of immune system Low molecular wt polypeptides (typically 10 to 40 KD ) secreted by ; lymphocytes ( effector T cells) APC’s Epithelial & mesenchymal cells in certain circumstances.

Cytokines (interleukins) : 

Cytokines (interleukins) Lymphokines (Lymphocytes derived ) Monokines (Monocytes /macrophages derived ) Chemokines Chemo;-- chemotactic Kines;---cytokines Group of cytokines that can attract either macrophages or neutrophils to the site of infection produced by; various cells in the infected area ,such as endothelial cells & resident macrophages.

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