The Immune System

Why an Immune System? Defends the body against pathogens (disease-causing organisms), toxins, and cancer cells. Includes both non-specific and specific responses.

The Immune System

Non-specific Immunity Skin Ciliated/mucus membranes of respiratory tract trap and sweep away foreign particles Tears and saliva contain enzymes that break down bacterial cell walls Non-pathogenic bacteria of skin, mouth, intestines, vagina, etc. out-compete pathogens Macrophages consume all foreign material it encounters A macrophage engulfs rod-shaped bacteria

Specific Immunity Targets specific pathogens (bacteria, viruses, cancer cells, or infected body cells). Works by detecting antigens – foreign proteins on the surface of pathogens that induce a specific immune response. Includes cell-mediated and antibody-mediated responses.

Antigen Presentation

Cell-mediated Response Macrophages that have ingested pathogens present antigens on cell surface to helper T-cells. Helper T-cells can produce chemicals called lymphokines that may activate killer T-cells. Killer T-cells can bind to and kill infected cells.

Cell-mediated Response

Antibody-mediated Response Lymphokines from helper T-cells activate B-cells to become plasma B-cells. Plasma B-cells produce free antibodies into blood, bind to specific antigens causing them to clump together. This clumps pathogens making it easier for macrophages to consume them. Other B-cells become memory B-cells which can reactivate the immune system quickly upon reinfection.

Antibodies Bind to Antigens

Antibody-mediated Response

Inflammatory Response – an important nonspecific defense *phagocytes = macrophages

Allergies Allergies result from immune cells that over-respond to non-pathogenic substances. Allergens (pollen, dust, egg whites, etc.) stimulate mast cells to produce chemicals called histamines. Histamines produce symptoms associated with inflammation (itching, swelling, redness, etc.)

Late-stage rheumatoid arthritis; an autoimmune disorder Autoimmune Diseases When the immune system mistakes body cells for pathogens, the result is an autoimmune disease. Autoimmune disorders result in destruction of healthy tissues by killer T cells. Examples: Type 1 Diabetes, Rheumatoid Arthritis, Multiple Sclerosis, Lupus Late-stage rheumatoid arthritis; an autoimmune disorder

Immune Disorders are on the Rise

Vaccines Vaccines are solutions of killed, weakened, or disassembled pathogens. Vaccines stimulate production of antibodies and memory cells without infection or disease.