Defense Against Infectious Disease

Review Disease- a disruption of homeostasis Infectious disease- caused by a pathogen Pathogen- disease producing organism such as bacteria, viruses, fungi, protozoan

Innate immunity- non specific immunity Skin and body secretions Inflammation response Phagocytes Neutrophils Monocytes Macrophages (monocytes that have migrated into tissue Eosinophils Interferons- proteins that protect against viruses

Both activated by antigens: foreign proteins Acquired immunity- building up an immune response to a specific pathogen 2 types of responses: Both involve lymphocytes which circulate in blood and lymphatic system 1. Production of antibodies, called antibody or humoral immunity. 2. cellular, or cell mediated, immunity Both activated by antigens: foreign proteins

Lymphatic system- Collects tissue fluid and filters it through the lymph nodes and thymus Lymph nodes- help filter out and concentrate pathogens. Dense with lymphocytes

Antibody, aka Humoral, Immunity Macrophages eat bacteria- antigens are presented on surface Helper T cells bind to macrophage and is “activated.” Signals B cell lymphocyte to react and change into a plasma cell- a plasma cell makes antibodies Antibodies mark bacteria or other cells for death Some B cells turn into Memory B cells

Cell-mediated immunity Macrophage eats bacteria, presents antigen on cell surface. Helper T cell binds to macrophage- is “activated” Helper T cell stimulates another type of lymphocyte- Killer T cell (aka cytotoxic T cell) Killer T cells multiply and attack the pathogen directly- inject enzyme Perforin into bacteria or cell, which kills them. Release cytokines- signals rest of immune system to activate

Passive vs Active immunity Passive: Mother’s milk, placental transfer or plasma infusion Active- patient injected with a vaccine. A weakened, dead or incomplete portion of pathogen is injected, stimulating an antibody response History: first safe vaccine 1798 by Edward Jenner

HIV Human immunodeficiency virus Spread by direct contact of body fluids or blood Destroys Helper T cells It may take 8-10 years for symptoms to appear

What role do phagocytes play in defending the body against disease? What role does a lymph node play in defending your body against microorganisms? What is the difference between naturally acquired passive immunity and naturally acquired active immunity?