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The Immune System Dr. Jena Hamra
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Immune System 3 major functions 2 types of immune responses
Protects body from disease Bacteria, viruses, fungi, parasites ANTIGEN: Anything that causes immune response Remove dead or damaged tissue Recognizes and removes abnormal cells 2 types of immune responses Innate immunity Nonspecific, immediate Acquired immunity Specific, can take several days
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Anatomy of the Immune System
Lymphoid tissues Primary Bone marrow Thymus gland Secondary Spleen Lymph nodes Diffuse tissues Tonsils GALT
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Cells of the Immune System
Leukocytes Eosinophils Basophils/Mast cells Neutrophils Monocytes/Macrophages Lymphocytes Dendritic cells
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Cell Function GRANULOCYTES Eosinophils Basophils Neutrophils
Fight parasites Allergic reactions Basophils Release histamine, heparin Neutrophils Ingest and digest bacteria Most abundant WBC in blood Release pyrogens, mediators of inflammation
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Cell Function Lymphocytes Monocytes Dendritic cells Secrete antibodies
Memory cells Cytotoxic cells Monocytes Macrophages in tissue Primary scavengers Bacteria, tissue Antigen presenting cells Dendritic cells Recognize, capture antigen
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Innate Immunity Nonspecific response Physical barriers Phagocytes Skin
Mucous membranes Ciliated epithelium Phagocytes Macrophages and neutrophils Phagocytosis Receptor mediated Extravasation and diapedesis
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Chemical Mediators Inflammation Acute phase proteins
Cytokines from macrophages Chemotaxis Increase capillary permeability Fever Acute phase proteins Produced by liver Released early in immune response Opsonins, antiprotease
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Chemical Mediators Histamine Interleukins
Located in granules of mast cells and basophils Initiates inflammatory response Increase capillary permeability Edema Vasodilation Increased local blood flow Interleukins Interleukin-1 Secreted by activated macrophages Stimulates acute phase protein synthesis Induces fever Stimulates cytokine release
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Chemical Mediators Bradykinin Complement proteins Vasodilator
Stimulates pain receptors Complement proteins Cascade Formation of membrane attack complex Lipid soluble molecules Insert into pathogen membrane, form pores Cell lysis
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Acquired Immunity Selective reaction to a specific antigen
Mediated by lymphocytes Membrane receptors specific for particular ligand Same specificity = clones Clonal expansion First exposure to antigen Cells divide = new clones Produces effector cells and memory cells Second exposure to antigen Activation of memory cells
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Lymphocyte Cytokines Required for activation and normal immune response Interleukins Clonal expansion and differentiation Interferons Alpha and beta: activate pathways against viral infection Gamma: Activates macrophages
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Lymphocyte Subtypes B lymphocytes T lymphocytes Secrete antibodies
Helper T cells (CD4): Secrete cytokines required for development of immune response Cytotoxic T cells (CD8): Attack and destroy foreign cells Natural killer cells: Attack and destroy virally infected or cancer cells
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Antibody Secretion (Humoral Immunity
B cells Activated B cells Plasma cells Plasma cells secrete antibodies Primary and secondary antibody response Primary: Slower and and weaker IgM Secondary: Faster, more antibodies produced IgG
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Antibodies IgG IgM IgA IgE IgD 75%, Secondary response
Primary antibody response IgA Secretory: saliva, tears IgE Allergic responses IgD Cell surface receptor on B lymphocytes
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Antibody Structure Y shaped proteins 2 heavy chains, 2 light chains
Fab region: antigen binding sites
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Antibody Function Opsonins Make antigens clump
Coat antigens, facilitate phagocytosis Make antigens clump Activate other immune cells Cytotoxic T cells Phagocytic cells B lymphocytes Activate complement Activate mast cells
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Cellular Immunity T lymphocytes T cell receptor
Mature in thymus Require antigen presenting cells Cytotoxic T cells Helper T cells T cell receptor Required for recognition of antigen Major histocompatibility complexes Required for antigen presentation CD4 recognize MHC II CD8 recognize MHC I
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