Chapter 36-2: Defense Against Infectious Disease

Innate Immunity (non-specific) 1st line of defense (physical and chemical barriers) Skin Sweat Tears Saliva Membranes lining body passages Mucus Stomach acid urine Contain enzymes (lysozyme) that break down bacteria cell membranes and walls

2nd line of defense Infection starts (inflammatory response) Symptoms of inflammation Swelling Redness Pain Heat Damaged cells (mast cells) and WBC (basophils) release histamines to increase blood flow to area of infection

Warmth attracts phagocytes (WBC that engulf particles) Macrophages, Neutrophil, and Monocyte ingest bacteria that enter tissue Pus Mixture of phagocytes, dead cells, bacteria, and body fluids Pathogen destroyed, inflammation goes down, wound heals

Viral Infections Phagocytes cannot destroy viruses Interferons Viruses can multiply inside of a phagocyte Interferons Proteins made by cells that have been infected by the virus Interferon goes into neighboring cells Neighbor cells make antiviral proteins that prevent viruses from multiplying

Acquired Immunity (3rd line of defense) Two types of immune responses: Antibody immunity Cellular immunity Gradual build up of resistance White blood cells develop the ability to recognize, attack, and destroy foreign substances (antigens) WBC produce antibodies for each antigen that enters Controlled by the lymphatic system

Lymphatic System Helps defend against disease Maintains level of body fluids Lymph nodes filter pathogens from tissue fluids Also makes lymphocytes (WBC) Located in the tonsils, spleen, and thymus (gland above the heart)

Antibody (humoral) Immunity T lymphocytes (T cells) Made in bone marrow Helper T cell interacts with B cell to activate immune response B lymphocytes (B cells) Produced in bone marrow Activated by T cell Becomes a plasma cell and produces antibodies that are released into blood and tissue spaces Memory B cells stay in the blood stream to respond to a second attack

Cellular Immunity Cytotoxic (killer) T cells transformed from T cells Stored in spleen, tonsils, lymph nodes Do not form antibodies Travel to infection site Release enzymes to pathogens Antigens are lysed and die

Passive Immunity Active Immunity Acquire antibodies from another host Passed from mother to child Can come from injections of antibodies from an animal or human already immune to antigen Develops when body is directly exposed to antigens Can be induced by vaccines Dead, weakened or incomplete portions of antigens Causes immune response