Chapter 43 ~ The Body’s Defenses

Lines of Defense Pathogen- any virus or living organism capable of causing a disease. –Most pathogens that enter our body don’t cause disease –Why are antibiotics effective?

Phagocytic and Natural Killer Cells Macrophages enzymatically destroy microbes Are phagocytic leukocytes. Will change shape to surround and invader Self vs. not-self Non-specific immunity Natural killer (NK) cells destroy virus-infected body cells & abnormal cells

Specific Immunity Lymphocyctes leukocytes that produce antibodies B Cells (bone marrow), produce antibody T Cells (thymus) help activate B cells Antigen: a foreign molecule that elicits a response by lymphocytes, “not-self” proteins (virus, bacteria, fungus, protozoa, parasitic worms) Antibodies: produced by B cells, protein molecule we produce in response to a specific type of pathogen

Antibody Structure and Production Each antibody if different and specific for one type of antigen As a GROUP though very similar Antibodies are proteins and are Y shaped At end of fork is binding site- where antibody attaches to anitgen Because antigen is a protein on surface of pathogen, antibody becomes attached.

Antibody Production (cont) 1- specific antigen is recognized 2- specific B lymphocyte identified that can produce antibody to bind to antigen 3- B lymphocyte and several identical B cells clone themselves rapidly to increase numbers 4- now “army” begins antibody production 5- newly released antibodies in bloodstream finding antigen match 6- destroy pathogen 7- some clones antibody produce lymphocytes that remain in blood and give immunity for second infection= MEMORY CELLS

The Inflammatory Response 1- Tissue injury; release of chemical signals~ in blood plasma, have plasma proteins; 2 of them are prothrombin and fibrinogen…they are always present until called into action, also have platelets 2/3- Dilation and increased permeability of capillary~ - platelets adhere to damaged area clotting factors; thrombin 4- Phagocytosis of pathogens~

Clonal selection Effector cells: short-lived cells that combat the antigen Memory cells: long-lived cells that bear receptors for the antigen Clonal selection: antigen-driven cloning of lymphocytes “Each antigen, by binding to specific receptors, selectively activates a tiny fraction of cells from the body’s diverse pool of lymphocytes; this relatively small number of selected cells gives rise to clones of thousands of cells, all specific for and dedicated to eliminating the antigen.”

Induction of Immune Responses Primary immune response: called polyclonal. Why? Importance?..can’t separate the different antibodies produced Monoclonal antibodies are “pure” anitbodies Secondary immune response: immune response if the individual is exposed to the same antigen at some later time ~ Immunological memory

Monoclonal Antibodies How do we get them?

Immunity in Health & Disease Active immunity/natural: conferred immunity by recovering from disease Active immunity/artificial: immunization and vaccination; produces a primary response Passive immunity: transfer of immunity from one individual to another natural: mother to fetus; breast milk artificial: rabies antibodies..can’t wait to build up immunity

Abnormal immune function Allergies (anaphylactic shock): hypersensitive responses to environmental antigens (allergens); causes dilation and blood vessel permeability (antihistamines); epinephrine Autoimmune disease: multiple sclerosis, lupus, rheumatoid arthritis, insulin- dependent diabetes mellitus Immunodeficiency disease: SCIDS (bubble-boy); A.I.D.S.

Vaccines Fundamental principle of immunity: can’t be immune to a pathogen without being exposed at least once. Benefits vs. dangers