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

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

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

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

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

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 days after initial exposure Sickness ensues awaiting max immune response

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

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