Immune System Pathogen agent that causes disease Nonspecific defenses First line of defense skin mucous membrane secretion of skin and muscle membranes a physical barrier is merely preventative Second line of defense phagocytic white blood cells defensive proteins the inflammatory respons The lymphatic system Specific defenses the immune system Third line of defense lymphocytes antibodies the lymphatic system Internal nonspecific defenses White blood cells a class of blood cells critical to immune function Phagocytes cell eating 1 Neutrophils engulf bacteria viruses 2 macrophages big eater Inflammation a localized tissue response nonspecific second line of defense Mast cell release histamine which causes dilation of capillaries increased blood flow increased permeability Phagocytes remove bacterial and dead tissue Immunity a log lasting protection resulting from a reaction of specific defenses to foreign pathogens Antigen any foreign substance that elicits an immune response Antibody any immune system protein that binds to a particular antigen Acquired immunity acquired resistance to infection active immunity antibodies that develop in our bodies in response to antigens long term passive immunity produced by transfer of antibodies from another source short term Innate immunity inborn resistance to infection Vaccine an antigen containing preparation that increases immunity to certain diseases by inducing formation of T and memory B cells vaccines elicit a response from the immune system B and T cells each start out as white blood cells originating in bone marrow B cells Humoral immunity secrete antibodies which mark invaders T cells cell mediated immunity attack infected cells A variety of B cells encounter an antigen antibodies are pre made and waiting for action This triggers production of more of these specific B cells Antibodies on the cell surface proliferate and enter the lymph and blood as free circulating antibodies Memory cells long lived lymphocytes formed during primary immune response Remain in lymph until activated by exposure to the same antigen that triggered its formation Cell mediated Immunity T cells a reaction to pathogens that have already entered cells microbe goes to macrophage which goes to antigen from the microbe and creates a self protein then fragments of the pathogen are displayed by the cell s self protein which then create a T cell receptor which then turns into a helper T cell Cell division makes 1 more activated T cells 2 B cells 3 cytotoxic T cells attack on infected cells Cytotoxic T cells How they work 1 Cytotoxic T cells binds to infected cell 2 perforin makes holes in infected cells membrane 3 proteins enter target cell through hole 4 kill infected cells Allergies a milder response to an antigen allergen 1 allergens enter bloodsteam 2 B cells make antibodies 3 antibodies attach to mast cell sensitization initial exposure to allergen 4 allergen binds to antibodies on mast cell 5 Histamine is released causing allergy symptoms later exposure to same allergen The common cold is caused by a virus The heat and redness that characterize inflammation are caused by the influx of fluids from leaky blood vessels to infected tissues T cells develop in the thymus Antibodies are produced by B cells
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