CHAPTER 43 THE BODY’S DEFENSE

I. Nonspecific mechanisms A.Skin & Mucous Membranes * physical & chemical (skin 3-5 pH) * saliva, tears & mucus; perspiration * nostril hairs

B.Phagocytic White Cells & Natural Killer Cells * neutrophils: cells that become phagocytic in infected tissue * monocytes: become macrophages (phagocytize microbes) * easinophils: against larger invaders (like worms)

C.Antimicrobial Proteins * complement system: cause lysis of microbes * interferons: inhibit viral reproduction; good against short term; made with recombinant DNA

D.The Inflammatory Response * caused when damage to tissue * vasodilation = increase blood flow & redness (caused diffusion of fluid = edema) * chemical signals initiate = histamine (vasodilation) & prostaglandins (increase blood flow) * migration of phagocytic cells * more widespread response can occur in severe case (appendicitis) * fever due to toxins or leukocytes

II. Defense of specific invaders A.Key Features of Immune System Specificity * antigen = foreign substance that elicits immune response * antibody = antigen-binding proteins Diversity: responds to different invaders Memory: recognizes previously encountered antigens (acquired immunity) Self/Non-Self Recognition

B.Active vs. Passive Acquired Immunity * active = recovery from disease (artificial w/ vaccine) * passive = transferred from one individual to another (pregnant) ; temporary

C.Humoral Immunity & Cell-Mediated * humoral = produce antibodies in response to toxins, free bacteria in body fluids * cell-mediated = intracellular; bacteria, cancer, transplants (depends on direct action of lymphocytes)

D.Cell of Immune System * 2 main classes of lymphocytes: 1. B cells: humoral (antibodies) 2. T cells: cell-mediated * kept in lymph organs

III. The immune system’s capacity to distinguish self from nonself is critical in blood transfusion & transplants A.Blood Groups * ABO blood groups = nonself recognition (antigen present on surface of RBC’s = not antigenic to that person but may be foreign to another) A has A antigen & make anti-B antibodies

Blood group antibodies --- agglutinate AB = universal recipient O = universal donor (not bad for fetus --- these antibodies can’t cross)

Rh factor - problem when mother is negative & baby is positive * mother makes antibodies when blood crosses usually only a problem in 2 nd child * Rh antibodies can cross placenta & destroy RBC’s of fetus * receive anti-Rh antibodies which destroy positive red cells before mother develops memory

B.Tissue Grafts & Organ Transplants * MHC (proteins embedded in plasma membranes of cells) = biochemical fingerprint unique to each individual - complicates tissue grafts & organ transplants

IV. Abnormal immune function leads to disease states A.Autoimmune disease: immune system reacts against self * some cases = immune reactions against components of own cells = lupus * rheumatoid arthritis = inflammation damages cartilage & bones in joints * destruction of insulin-producing pancreas cells = insulin-dependent diabetes

B.Allergy: hypersensitivity of body’s defense to environmental antigens (allergen) * IgE antibodies recognize pollens as allergens * antihistamines used to treat (histamines cause dilation & increased permeability of small blood vessels)

Anaphylactic shock = life-threatening reaction to injected antigens (sudden dilation = decrease blood pressure; death in a few minutes); epinephrine may be injected

C.Immunodeficiency: * individual is inherently deficient in either humoral or cell-mediated immune defenses * not all inborn: Hodgkins disease (cancer damages lymphatic) or physical & emotional stress (adrenal hormones) * direct links between nervous & immune system

D.Acquired Immunodeficiency Syndrome * infection from HIV * reduction of T cells – causes secondary infection * may remain as a provirus before becoming active * not eliminated by antibodies because: latent provirus, mutate, no T-cells