Innate Immunity

1. Innate Immunity • Present before exposure to pathogens • Present at birth • Non-antigen specific • Consists of: • Skin… barrier for microbes and viruses • Compromised by abrasion or laceration • Sebacious sweat is acidic (pH 3-5)… prevents colonization of bacteria • Mucus membranes… secrete mucus to trap microbes • Mucocilliary escalator moves trapped microbes out of the trachea • Secretions contain lysozyme, an enzyme, to digest the walls of bacteria

2. Innate Immunity • Phagocytic cells • Mediate inflammation to limit the spread of microbes • Contain antimicrobial proteins that bind to the surface of bacteria • Once engulfed the phagocyte fuses a lysosome to the vacuole containing the bacteria • Some bacteria evade phagocytes by hiding surface recognition via a capsule • Types: • Neutorphils… 60-70% of all WBCs • Attracted to infection • Sacrifice themselves after phagocytosis • Macrophages… ~5% (developed from monocytes) • Attack microbes trapped in the lymph system and various other organs • Eosinophils… active against multicellular invaders • Inject enzymes to damage organism • Dendritic cells… stimulate acquired immunity after ingestion of cells

3. Innate Immunity • The compliment system consists of over 30 proteins that when activated attack organisms and activate the immune system • Initiated be lysozyme • Interferon… limits viral replication in cells neighboring an infected cell • Non-specific • Inflammatory response… due to injury of pathogens • Created by histamine release from mast cells in the epithelium • Cause swelling of capillaries and increased blood flow that leaks fluid into tissues bringing macrophages • Discharge of prostaglandins that further promotes blood flow • Release chemokines that direct phagocytes to the infected area

4. Innate Immunity • Natural Killer Cells • Patrol the body looking for infected cells. • They attack and cause cell death through apoptosis • Evaded in some viral infections and cancer

5. Acquired Immunity • Often called adaptive immunity • Developed only after exposure • Highly specific

6. Lymphocytes… key cells in acquired immunity • Activated by the presence of cytokines • Antigens (foreign particles) elicit the immune response • Epitote… small part of the antigen molecule that is recognized by a specific lymphocyte • Each lymphocyte may contain up to 100,000 identical epitote recognition sites • Activation causes immediate clonal response producing 2 additional cells… 1 being a memory cell • Called the primary immune response • Maximum response 10-17 days after initial exposure • Sickness ensues awaiting max immune response

7. Acquired Immunity • B-lymphocytes… recognize and bind to intact surface antigens • Developed in the bone marrow from pluripotent cells • Secrete antibodies • Bind to antigens to mark for elimination • Shorten subsequent infections • Called the secondary immune response

8. Acquired Immunity • T-lymphocytes… similar to B-lymphocytes but can bind to smaller epitotes called MCH molecules • Originate in the bone marrow but mature in the thymus gland • Class 1 MCH… found on almost every cell in the body • Are presented when the cell becomes infected signaling the cytotoxic (killer) T-cells • Class 2 MCH… presented by macrophages, dendritic cells, and B-cells through antigen-presenting. • Signals the helper T-cells