Immune System Nonspecific Immunity Specific Immunity Defense system

Immune System

Nonspecific Immunity Specific Immunity Defense system

First line of defense: Surface membrane barriers • Skin and mucous membrane – Layered epidermis and shedding of epithelial cells – Sebum inhibits growth of bacteria and fungi – Mucous traps microbes, dust and pollutants. • • • Lacrimal apparatus Saliva Vaginal secretions Flow of urine Defecation and vomiting Gastric juices destroy bacteria and their toxins

Text Table 21. 2 Oral Cavity Antimicrobial enzymes in saliva (e. g. lysozyme and lactoperoxidase) inhibit microbes, Resident flora Skin p. H (3 -5), sebum Respiratory Cavity Hairs, cilia, mucociliary escalator, Sticky mucus (lysozyme) traps dust and microbes. GI Tract low p. H and digestive enzymes, flushing action Eyes Tears, (lysozyme). flushing action Vagina p. H, flushing action, resident flora

Second line of defense: chemical and cellular defenses • Antimicrobial proteins – Interferon – Complement – Transferrins • Natural killer cells • Phagocytes – Neutrophils – Dendritic cells – Macrophages • Wandering • Fixed – Eosinophils

Interferons • Produced by lymphocytes, macrophages and fibroblasts. • Interfere with translation of viral proteins • Degrade viral RNA • Activate macrophages and NK cells • Interferon Animation

Complement Cascade Animation

Phagocytosis

Phagocyte Mobilization

Fever • Regulated my hypothalamus • Due to pyrogens secreted my leukocytes & macrophages • Causes liver and spleen to sequester zinc and iron • Increases metabolic rate (repair)

Inflammatory response Stages Inflammation Animation • Release of Chemical Alarms • Vasodilatation & Permeability of BV • Emigration of phagocytes: Dispose cellular debris & pathogens • Sets the stage for repair • Prevent spread of damaging chemicals & pathogens Signs of inflammation – – – Redness Heat Swelling Pain Impairment of function

Comparison of Immune Cells

Adaptive Resistance • Specificity—recognition of particular antigens • Memory—remembers previously encountered antigens • Systemic—immunity is not restricted to the initial infection site • Immune responses – Antibody-mediated or humoral immune responses (late 1800 s) – Cell-mediated immune responses (mid 1900 s)

T Lymphocytes • CD 4 T cell - also known as a T Helper (Th) cell • CD 8 T cell - also known as a Cytotoxic T (Tc) cell

Antigens and antigen receptors • Antigens can be entire microbes, parts of microbes or chemical components of pollen, egg white, blood cells, …….

Self antigens: MHC proteins • Antigens on our own cells are self-antigens • MHC proteins are glycoproteins that mark the cell as self. – Class I MHC proteins are on all body cells. Receptors on TC – Class II MHC proteins are only on certain cells that act in the immune response. Receptors on TH – Antigen Processing

Immunocompetence • T and B cells that have not been exposed to an antigen are naïve. • Binding with an antigen completes differentiation into functional B and T cells. • B cells mature in the bone marrow. • T cells mature in the thymus.

Antigen receptors • Genes determine what foreign substance will be recognized. • An antigen determines which T or B cells will be activated. • Lymphocytes make over a billion different receptors. • Gene segments of a few hundred bits are reshuffled and combined--somatic recombination. • The newly assembled gene is expressed as a receptor on the cell surface.

Humoral immune response • Antigen challenge—the meeting between a naïve immunocompetent lymphocyte and an invading antigen. • Occurs in lymphoid tissue such as spleen or lymph node. • If antigen challenge is presented to a B cell then the humoral immune response is provoked.

Clonal Selection Monoclonal Antibody Production

Antibodies “immunoglobulins”

Immunoglobulin classes • Ig. D is attached to B-cell plasma membrane • Ig. M is released during primary response. Indicates current infection. • Ig. G is the most aboundant. Can cross placenta & blood vessel walls. • Ig. A found in body secretions prevents attachment to body surfaces. • Ig. E causes release of histamine (allergies) by attaching to mast cells & basophils.

Immunological memory • Primary immune response • Secondary immune response

Antibody defense: PLANe • Precipitation • Lysis: Complement fixation and activation • Agglutination • Neutralization • Enhancing phagocytosis

Cell-mediated immunity • Antibodies can only inactivate an antigen and NOT destroy it. • Antibodies prepare an organism for destruction by innate defenses. • T cells can only recognize and respond to processed fragments of protein. • T cells are suited for cell to cell interaction and target body cells infected by virus, bacteria and abnormal or cancerous body cells or cells that are transplanted or infused.

Cell-mediated immunity: T-cells • Activation of T cells—T cell receptors bind to antigen presented by the antigen-MHC complex. • CD 4 and CD 8 proteins interact with antigen and help maintain MHC-antigen coupling. • Types of T-cells – Helper T cells (CD 4) – Cytotoxic T cells (CD 8) – Memory T-cells

Activated T cell • Activation leads to enlargement, differentiation and proliferation of T cells. • T cells that are reproduced are clones of originally activated T cell. • Activation, differentiation and proliferation occurs in secondary lymph organs and tissue. • Activation leads to release of inflammatory cytokines.

Homeostatic imbalances : Immunodeficiencies • Abnormally behaving immune cells • Severe combined immunodeficiency (SCID) syndromes – Congenital conditions • Acquired immune deficiency syndromes – Hodgkin’s Disease – HIV – AIDS

Homeostatic imbalances : Autoimmune disease – Tend to be more prevalent in women • Type I diabetes—destroys pancreatic beta cells • Multiple sclerosis—destroys myelin sheaths • Myasthenia gravis—impairs communication between nerve and muscle • Lupus erythematosus—systemic disease of skin, kidneys, heart, and lungs • Rheumatoid arthritis—destruction of joints

Organ transplants • Autografts—grafts from the same person to another body site • Isografts—grafts between genetically identical individuals • Allografts—grafts among the same species • Xenografts—grafts taken from another animal species

Hypersensitivities Hypersensitivity Reactions in the Skin

Hypersensitivities Acute Immediate Subacute cytotoxic Subacute Immune complex Delayed

Type I Hypersensitivity Animation Type II Hypersensitivity

Type III Hypersensitivity

Animations • Flash animation of a NK cell interacting with a normal body cell. • Flash animation of a NK cell interacting with a virus-infected cell or tumor cell not expressing MHC-I molecules. • Flash animation of apoptosis by NK cells. • HIV Replication

Resources • Components of the Immune System Animation