Immune Systems Introduction to Immune Systems A. Infection 1. Invasion by foreign organisms a. Viruses, fungi, bacteria B. Immunity 1. Long term resistance to reinfection by organisms reviously encountered a. Cell-mediated immunity (1) Leukocytes attack “nonself” materials b. Antibody-mediated immunity (1) Highly specific proteins that bind to “nonself” materials C. Antigens 1. Any material that elicits an immune response a. Immune responses are usually directed against foreign proteins 2. In some diseases the body recognizes “self” proteins as foreign and attacks them a. Rheumatoid arthritis Nonspecific Protective Mechanisms A. Physical Barriers 1. Skin and mucous membranes B. Biochemical Barriers 1. Stomach acid 2. Enzymes in saliva, tears and sweat C. Inflammation 1. Phagocytosis a. Cells engulf foreign materials b. Pus is evidence of phagocytosis Immunity - Specific, Long Lasting Protection A. Edward Jenner and Smallpox (1798) 1. Observation a. Milk maids who got cowpox were resistant to cowpox 2. Experiment a. Injected a boy with pus from cowpox sores 3. Results a. Boy was protected against smallpox B. Vaccines 1. Killed or altered versions of a virus may provide longterm immunity against that virus a. Measles Mumps Rubella Smallpox Pertussis Diphtheria Polio Hepatitis Rabies
Lymphocytes A. Production of Lymphocytes 1. Bone Marrow a. Makes a variety of B cells 2. Thymus a. Makes a variety of T cells B. B Cells 1. Produce antibodies C. T Cells 1. Killer T Cells a. Cell mediated immunity 2. Helper T Cells a. Interact with B cells to produce antibodies (1) Primary target of HIV is a Helper T Cell (T4) 3. Suppressor T Cells a. Interact with B cells to suppress antibody production Cell Surface Receptors A. B Cells 1. Have antibodies on their surface identical to the one that they produce 2. Each B cell can make only one antibody B. The Immune Dilemma 1. Humans can respond to millions of different antigens 2. Millions of different antibodies should require millions of different genes 3. There are only 100,000 genes in the human genome Premade Antibodies A. Clonal Selection 1. Each B-Cell produces only one antibody a. All descendents will produce the same antibody B. Primary Immune Response 1. Rapid increase in number of specific B cells after antigen exposure 2. Plasma cells begin large scale manufacture of antibodes C. Secondary Immune Response 1. Exposure to antigen after Primary response a. Long lived B cells (Memory Cells) quickly produce large quantities of antibodies to prevent illness
A Family of Antibody Proteins A. Function of Antibodies 1. Bind to foreign antigens 2. Begin processes that destroy the antigen B. Antibody construction 1. Two identical Light chains a. One constant region b. One variabel region 2. Two identical Heavy chains a. One constant region b. One variable region Antibody Diversity A. Lock Analogy 1. Combination numbers 0 - 10 a. one number = 101 (10) combinations b. two numbers = 102 (100) combinations c. three numbers = 103 (1000) combinations B. Light Chain Heavy Combinations 1. Suppose 1000 genes for each a. 10002 combinations = 106 (one million) possible antibodies
Malfunctions and Disease A. Causes of Malfunctions 1. Infections a. AIDS 2. Stress 3. Poor nutrition 4. Drugs B. Hypersensitivity 1. Antibody response to antigens causes release of histamines a. Antigens (1) pollen, dander, foods, insect venom b. Histamine effects (1) Sneezing, itchiness, watery eyes (2) Constriction of airways leading to asthma 2. Hypersensitive reactions tend to get worse with repeated exposure to the antigen C. Autoimmunity 1. Immune system attacks self a. Rheumatoid arthritis b. Multiple Sclerosis c. Diabetes 2. Mechanisms of autoimmunity are not well understood