The Immune System Dr. Jena Hamra

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

Anatomy of the Immune System Lymphoid tissues Primary Bone marrow Thymus gland Secondary Spleen Lymph nodes Diffuse tissues Tonsils GALT

Cells of the Immune System Leukocytes Eosinophils Basophils/Mast cells Neutrophils Monocytes/Macrophages Lymphocytes Dendritic cells

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

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

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

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

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

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

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

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

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

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

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

Antibody Structure Y shaped proteins 2 heavy chains, 2 light chains Fab region: antigen binding sites

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

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