Body’s Defenses

Passive Formation of antibodies To the fetus thru the placenta, thru breast milk, thru administration of plasma (artificial) Active Formation of your own antibodies Vaccinations by contracting an infectious disease by exposure of an antigen

Innate immune systemAdaptive immune system Response is non-specificPathogen and antigen specific responseantigen Exposure leads to immediate maximal response Lag time between exposure and maximal response Cell-mediatedCell-mediated and humoral componentshumoralCell-mediatedCell-mediated and humoral componentshumoral No immunological memoryimmunological memoryExposure leads to immunological memory Found in nearly all forms of lifeFound only in jawed vertebratesjawed vertebrates Components of the immune system

Non-specific Specific

Nonspecific defense mechanisms are general and protect against many types of pathogens Barriers to entry Inflammatory rxns Protective proteins

Pathogens: bacteria, fungi, protozoa, and viruses that cause infection

Physical barriers prevent pathogens such as bacteria and viruses from entering the organism.

Enzymes Acids: stomach acid

Complement System

1 st WBC to scence Phagocytes capable of diapedesis Hallmark of acute infection First to arrive on scene 40-70%

Mediate for allergies Limited phagocytic activity Strong Chemotaxis Attract to injury and infection Destroys Antigen/Ab complex 2-4%

Mast cells Releases histamine: vasodialator Heparine: anticoagulant Releases serotonin/Kinin.5-1% (smallest population)

Scavengers Transform into macrophages, eating bacteria, viruses and tissue debris 3 rd line of defense 3-8%

Acquired immune response SPECIFIC defense system 20-25% Forms 2 types: T cells: attack all foreign cells B cells: produce Ab to get rid of bacteria and viruses

Blood cells are produced in the bone marrow from a pluripotent stem cell that can become either a WBC, RBC or Platelet

Phagocytes

Immunity is a specific defense mechanism. It is resistance to a particular pathogen or its toxin or metabolic by- product. Immunity is based upon the ability to distinguish self molecules from non-self. Molecules that can elicit an immune response are antigens.

The lymphatic system responds to non-self or foreign antigens, but not to self antigens. Shape of antigens allow immune system to be specific Antigens: molecules that can elicit an immune response and each having their own receptor may be proteins, polysaccharides, glycoproteins, or glycolipids.

Macrophages alert lymphocytes by displaying antigens from engulfed cells. Foreign antigens are attached to the macrophage surface by a self protein, part of the major histocompatibility complex (MHC).

Helper T cells destroy infected cells and clean up pathogens T cells attach to foreign, antigen-bearing cells, cell-to-cell contact. Cytokines or lymphokines enhance cellular response to antigens.

Helper T cells produce chemical signals to activate cytotoxic T cells, which are WBC carrying pathogen-specific receptors on their surface Kill cancer cells and attack foreign tissue

Red bone marrow releases undifferentiated lymphocytes into the circulation. Some become T lymphocytes or T cells in the thymus. Figure 16.16

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B cells secrete antibodies into the blood: antibody-mediated immunity. Helper T cells activate B cells in response to macrophage presentation of antigens. Stimulated B cells produce plasma cells or memory cells. Plasma cells produce antibodies.

AB are released by plasma cells and circulate in blood and lymph Ab attach to pathogens, similar to specific binding of cytotoxic T cells AB/Antigen complex are then destroyed by general defense like macrophages or proteins that puncture pathogen’s membranes

Helper T cells stimulate B cells to produce antibodies CD4 cells are prime targets of HIV Memory T cells produced upon initial antigen exposure and protect against delay in future exposure Cytotoxic T cells release perforin to destroy cells that present foreign antigens

Activated helper T cell releases cytokines. Cytokines stimulate B cell proliferation. Figure 16.19

Some B cells become plasma cells that secrete antibodies that bind antigens. Antibodies (immunoglobulins) are globular proteins composed of four chains. Ends of the molecule contain antigen-binding sites.

Memory Cells

Vaccines

How pathogens evade immunity Antigen shifting

Immunoglobulin G IgG, gamma globulin, 80% of antibodies defends against bacteria, viruses, toxins found in blood plasma and tissue fluid activates complement Figure 16.20

Immunoglobulin A IgA, 13% of antibodies found in exocrine secretions defends against bacteria and viruses

Immunoglobulin M IgM, 6% of antibodies, found in plasma activates complement Immunoglobulin D IgD, found on mast cells activates B cells Immunoglobulin E IgE, found in exocrine secretions promotes inflammation and allergic reactions

Antibodies attach directly to antigens agglutination, precipitation, neutralization Antibodies activate complement Combination with antigens exposes reactive sites on complement which results in opsonization increasing phagocytosis susceptibility chemotaxis attracting neutrophils and macrophages inflammation to prevent spread of antigens lysis of cell membranes

Humoral

Cellular Barriers

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