The Immune System

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The Immune System

• Dr. Jena Hamra

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Immune System

• 3 major functions
• 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
• 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
• Secrete antibodies
• Memory cells
• Cytotoxic cells
• Monocytes
• Macrophages in tissue
• Primary scavengers
• Bacteria, tissue
• Antigen presenting cells
• Dendritic cells
• Recognize, capture antigen
• Antigen presenting cells

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Innate Immunity

• Nonspecific response
• Physical barriers
• Skin
• Mucous membranes
• Ciliated epithelium
• Phagocytes
• Macrophages and neutrophils
• Phagocytosis
• Receptor mediated
• Extravasation and diapedesis

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Chemical Mediators

• Inflammation
• 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
• 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
• Increase capillary permeability
• Stimulates acute phase protein synthesis
• Induces fever
• Stimulates cytokine release

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Chemical Mediators

• Bradykinin
• 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
• Secrete antibodies
• T lymphocytes
• 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
• 75, Secondary response
• IgM
• 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
• 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
• 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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