BI 103 Lecture Notes: Chapter 32 Immune System: Defense against Disease

I. Barriers (External Defense)

            A) Skin

                        1. dry, nutrient free zone         2. natural antibiotics    3. skin continually replaced

            B) Mucous Membranes (Line digestive, respiratory, urogenital tracts: produce mucus)

                        1. Secrete mucus to trap enzymes, contains antibacterial enzymes

                        2. Cilia sweep up mucus

II. Non- specific Internal Defenses

            A)  Phagocytic Cells: Engulf bacteria, damaged cells by phagocytosis

                        1. Macrophages                      2. Neutrophils

            B) Natural Killer Cells: disrupt cell membranes of invaders

            C) Inflammation: Damaged cells

                        1. Signal mast cells to release histamine

                        2. Initiate blood clotting

                        3. Attract macrophages and neutrophils

                        4. Signal pain to CNS

            D) Fever

                        1. Increases macrophage activity and antibody production

                        2. Slows bacterial reproduction

III. Specific internal defenses: Immune Response

            A) Key Players: specialized leukocytes = lymphocytes  (see table 32-1)

                        1. B Cells                    2. T Cells

            B) Fundamental Steps in the Immune Response

                        1. Immune system must recognize invader

                                    A. Antigens: molecules located on surface of cells which triggers an                                               immune response (on bacteria, on infected body cells, full macrophages)

                                                1. B cells produce antibodies which recognize antigens

                                                            a. “Y” shaped proteins, high specificity binding site

                                                2. T cells produce T-cell receptors (stay bound to T cell)

                                    B. Body recognizes “self” cells via major histocompatibility complex

                                                1. unique sets of proteins/polysaccharides on cell surface

                        2. Immune system must launch attack

                                    A. Humoral immunity (B cells and circulating antibodies)

                                                **attack microbes before they have invaded body cells

                                                1. B cell antibody receptor binds antigen

                                                2. Now activated B cell divides rapidly (clonal selection)

                                                            a) produces memory cells

                                                            b) produces plasma cells (antibody factories)

                                                3.  Antibodies destroy invaders (and attract phagocytic cells)

                                                            a) inactivate invader by binding all over it

                                                            b) clump invaders together

                                                            c) coat invaders with blood proteins

                                                            d) all of these increase phagocytic cell activity

                                    B. Cell mediated immunity

                                    (Three types of T cells, produced after receptor on T cell binds to antigen)

                                                **Attack microbes after they have invaded body cells

                                                1. Cytotoxic T cells: work like natural killer cells

                                                2. Helper T cells: stimulate immune cell division

                                                3. Memory T cells: persist past infection

                        3. Immune system must remember past victories

                                    A. Memory cells “remember” specific antigens

                                    B. Respond rapidly to repeat invasion

IV. Medical Care Augments Immune Response

            A)  Antibiotics:  Slow down microbial (NOT VIRUSES) reproduction

            B)  Vaccinations: Inject weakened/killed microbes: stimulate memory cell production

V. Malfunctions of the immune system

            A) Allergies: B cells recognize harmless substances as antigen

            B) Autoimmune diseases

                        1. Type I Diabetes

                        2. Multiple Sclerosis