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THE IMMUNE SYSTEM
We are constantly exposed to an incredible diversity of bacteria, viruses, and parasites
How does the immune system protect us?
The key isour ability to produce more than 108 distinct antibodies and more than 1012 T-cell receptors
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The immune system has 2 arms
Innate immunity
Adaptive immunity
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The Immune System is the Third Line of Defense Against Infection
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Immune response
• The specific reactivity induced in a host by an antigenic stimulus
2 TYPES:
1. Humoral (AMI)
2. Cellular (CMI)
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LYMPHOCYTES INVOLVED IN THE IMMUNE RESPONSE
B lymphocytes T lymphocytes
Mainly derived from bone marrow
T lymphocytes are of thymic origin
HUMORAL IMMUNITY CELLMEDIATED IMMUNITY
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• The production of antibodies consists of 3 steps
Humoral Immune response(AMI)
Entry Processing Secretion
Afferent limb Central limb Efferent limb
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Antibody production follows a characteristic pattern
Lag phase Log phase Plateau or steady state
Phase of decline
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ANTIBODY RESPONSE AFTER EXPOSURE TO ANTIGEN
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Fate of antigen in tissues
Antigen Introduced I.V SPLEEN
LIVER BM
KIDNEY LUNGS
Broken down by RE cells
70-80% Excreted in the urineEliminated within 1 or 2 days
Introduced S.C
Draining lymph nodes
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Fate of antigen in tissues
• Antigens are removed from circulation in 2 phases
Non-immune phase Phase of immune elimination
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PRODUCTION OF ANTIBODIES
• Immune response to an antigen is brought about by 3 type of cells
APC T-cells B-cells
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ANTIGEN-PRESENTING CELLSCapture
Display
Signal
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ANTIGEN-PRESENTING CELLS
Macrophages
Dendritic cells
B lymphocytes
Follicular dendritic cells
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Major Histocompatibility Complex
• The task of displaying cell-associated antigens for recognition by T cells is performed by specialized proteins that are encoded by genes in a locus called the MHC
2 TYPES
Class I MHC
Class II MHC
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Major Histocompatibility Complex
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Major Histocompatibility Complex
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Lymphocytes
B - Lymphocytes HUMORAL IMMUNITY
T - Lymphocytes CELL MEDIATED IMMUNITY
Helper T cellsCytotoxic T cellsNK cells
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Lymphocytes
• Provides 2 defining characteristics of the adaptive immune response,
1.Specificity
2. Memor
y
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T Cells Only Recognize Antigen Associated with MHC Molecules on Cell Surfaces
T cell recognize with the help of T cell receptor
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T CELL RECEPTOR
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Central Role of Helper T Cells
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CYTOTOXIC T CELLS LYSE INFECTED CELLS
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Humoral Response to Antigens
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Factors influencing antibody production
Genetic Age Nutrition
Route of administration
Size & number of doses Multiple antigens
Adjuvants Immunosuppressive drugs Effect of antibody
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CELLULAR IMMUNE RESPONSE (CMI)
Specific immune response that do not involve antibodies.
Delayed hypersensitivity
Immunity in infections
Transplantation immunity
Immunological surveillance
Autoimmune disease
Scope of CMI
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Induction of CMI
• Antigenic stimulus• Only T-cell dependant antigens lead to CMI• T-cell bears specific receptor on its surface• T cells recognize antigens only when
presented with MHC molecules• Helper T-cells• Cytotoxic T-cells
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CYTOKINES• Biologically active substances released by
activated T lymphocytes were called LYMPHOKINES
• Similar substance produced by Monocytes Macrophages
MONOKINES
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CYTOKINES•MIF• MAF• MCF
Affecting macrophages
•BF/MF• TGF•BGF
Affecting lymphocytes
•CF•CSF
Affecting granulocytes
•LT•IFN•TNF
Affecting cultured cells
•SRF•TFOthers
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CYTOKINES - CLASSIFICATION•IL-1•IL-2•IL-3…13
Interleukins
•GM-CSF•G-CSF•M-CSF
Colony stimulating factors
•TNF-α•TNF-β
Tumour necrosis factors
•IFN-α•IFN-β•IFN-γ
Interferons
•TGF-β•LIFOthers
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Cytokines • Peptide mediators or intracellular messengers
which regulate immunological, inflammatory and reparative host responses
• They are potent hormone like substances
• Produced by lymphocytes, macrophages, platelets & fibroblasts
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Cytokines
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• Source: Macrophages & other cells• IL-1α and IL-1β• Functions: Proliferation & differentiation of T, B and other
cells Pyrogenic Induce acute phase proteins Bone marrow cell proliferation
Interleukin-1 (LAF)
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• Source: T-cells• Powerful modulator of the immune response• Functions: Promote growth and differentiation of T and B
cells Cytotoxicity of T and NK cells Secretions of other lymphokines
Interleukin-2[TCGF]
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Interleukin-2[TCGF]
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Other interleukins
Interleukin-3 (multi-CSF) Growth factor for bone marrow stem cells
Stimulates hematopoiesis
Interleukin-4 (BCGF-I) Differentiation and proliferation of B and T cells
Enhances the activity of cytotoxic T cells
Activates mast cells
Interleukin-5 (BCGF-II) Proliferation of activated B cells
Induces maturation of eosinophils
Interleukin-6 Induces immunoglobulin synthesis by activated B cells
Induces formation of IL2 receptors on T cells
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• Stimulates the growth & differentiation of pleuripotent stem cells in the bone marrow
• Responsible for adjusting the rate of production of blood cells
• Treating hematopoietic dysfunctions in infections & malignancies
Colony stimulating factors
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• Induce hemorrhagic necrosis in certain tumours
• 2 types: TNFα and TNFβ• Cachectin is TNFα
Tumour necrosis factors
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• Originally identified as antiviral agentsα-Produced by leucocytesβ-Produced by fibroblastsγ-Produced by T-cells• Functions: Macrophage activation Antitumour activity
Interferons
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Kuby IMMUNOLOGY
Fifth Edition
REFE
REN
CES
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