The Immune System

Functions of the Immune System defense mechanism against illness. distinguishes between yourself, germs, and the outside world consists of the thymus , spleen, Lymph nodes, bone marrow ,white blood cells , antibodies, complement system and hormones

I. 1st Line of Defense: Skin and Mucus Membranes Skin Surface (keep’em out) 1. Dry, dead, thick, secretions 2. Sweat and sebaceous glands: release antibiotics, lactic acid, Rnase (flush away and create acidic environment) B. Mucus (move’em out) 1. Antibacterial enzymes (e.g. lysozyme) 2. Entraps – hairs and cilia (in respiratory tract) move out unwanted materials) a. stomach pH destroys b. stomach and intestinal enzymes break down

II. 2nd Line of Defense: Non-Specific Internal Defenses Cells 1. Phagocytic Cells (Eat’em up) a. White Blood Cells b. Macrophages - engulfing behavior 2. Natural Killer Cells (Blow'em up) a. recognize body cells infected with foreign bodies (i.e. viruses) b. transfer membrane containing "hole-forming" proteins c. secrete enzymes

Natural Killer cells

B. Antimicrobial Proteins 1. Complement System (Poke holes in'em) a B. Antimicrobial Proteins 1. Complement System (Poke holes in'em) a. group of 20+ proteins produced by neutrophils b. activated in a progressive (cascade) fashion; c. lyse invading microbes. d. some proteins attract phagocytes. 2. Interferons (Harass'em) a. produced by viral infected cells, help neighbor cells that inhibit viral replication b. three types: alpha, beta, gamma c. pre-antibody response - early response to short- term infections d. gamma activates phagocytes

C. Inflammatory Response 1. Damaged cells release histamine a C. Inflammatory Response 1. Damaged cells release histamine a. histamine makes capillary walls leaky b. relaxes smooth muscle c. result: blood flows into wounded area: inflammation and increased delivery of WBCs, platelets, etc. 2. Clotting response - chemically stimulated by wounded cells causing an attraction of phagocytic WBCs - produces pus 3. Fever (Cook’em) a. controlled by hypothalamus (set point: 37oC). b. inhibits bacteria metabolism c. stimulates phagocytic WBCs d. increases production of interferon in viral attacks *Note -aspirin reduces fever; prolongs viral (flu) infections

Response to Injury

III. 3rd Line of Defense: Immune Response B-Cell Defense - Response to extracellular invaders 1. B-Cell Receptors - Antibodies a. Y-shaped structure b. many different kinds c. each specific to a particular antigen 2. Helper T-cells stimulate the activation of B-cells 3. Activated B-Cells differentiate a. Plasma cells: secrete antibodies b. Memory cells: remain ready for future attack 4. Antibodies neutralize foreign body a. cover foreign body b. promote phagocytosis by covering body

B. T-Cell Defense – Response to intracellular invaders 1 B. T-Cell Defense – Response to intracellular invaders 1. Viral attacked cell ingested by macrophage a. Antigens on macrophage are recognized by Helper T-cell receptors b. Interleukin I is released which activates Helper T-cells 2. Activated Helper T-Cells activate Cytotoxic T-cells and Memory T-cell and release Interleukin 2 a. Cytotoxic T-Cells recognize invading antigens b. Memory T-cells are able to recognize an antigen if it reappears 3. Interleukin 2 activates B-cells a. Some B-cells form antibodies b. other B-cells become memory B-cells 4. Suppresser T-Cells turn off Immune Response

Antibody Immunity

Diseases of the Immune System Lupus - Lupus is an autoimmune disorder, which means the body's immune system attacks its own healthy cells and tissues. It is characterized by periodic episodes of inflammation and damage to the joints, tendons, other connective tissues, and organs, including the heart, lungs, blood vessels, brain, kidneys, and skin. Lupus affects each individual differently and the effects of the illness range from mild to severe. Lupus can potentially be fatal.

AIDS - a fatal disease of the human immune system caused by the human immunodeficiency virus (HIV). This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to infections and malignancies (tumors). HIV attacks the helper T-cells which are integral to the immune response.