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 invadersA. Key Features of Immune System

Specificity* antigen = foreign substance that

elicits immune response* antibody = antigen-binding

proteinsDiversity: responds to different invadersMemory: 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 2nd 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