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First Line of Defense includes skin, mucous membranes. not specialized for a particular invader. general defense against all kinds of pathogens. Skin physical barrier covered w/ oily & acidic secretions from sweat glands. pH 3-5. Antimicrobial proteins are contained in saliva, tears, & other secretions found on mucous membranes. ie: lysozymes. Lysozymes break down the cell walls of bacteria ("lyses" them). Cilia line the lungs to sweep invaders out of lungs. Gastric juice located in the stomach; kills most microbes. Symbiotic bacteria found in the digestive tract & vagina; outcompete many other organisms that could cause damage. Second Line of Defense involves several more nonspecific mechanisms. Phagocytes WBCs (leukocytes) that engulf pathogens by phagocytosis. includes Neutrophils, Monocytes, and Natural Killer cells. Monocytes enlarge into large phagocytic cells called macrophages. Natural Killer Cells attack abnormal body cells (tumors) or pathogen-infected body cells. Complement system a group of 20 proteins that help attract phagocytes to foreign cells and help destroy cells by promoting cell lysis. Interferons substances secreted by cells invaded by viruses that stimulate neighboring cells to produce protein that help them defend against the viruses. A protein that has antiviral or immune regulatory functions. Interferon-α and interferon-β, secreted by virus-infected cells, help nearby cells resist viral infection; interferon-g, secreted by T cells, helps activate macrophages. Inflammatory Response a series of nonspecific events that occur in response to pathogens. Includes Histamines, Vasodilation, Phagocytes, and Complements. Histamine secreted by Basophils. Basophils WBCs found in connective tissue. Vasodilation dilation of blood vessels. stimulated by Histamine, increases blood supply to damaged area, allows for easier movement of WBCs through vessel walls. causes redness, swelling, and increase in temperature (which stimulates WBCs making the enviro inhospitable to pathogens). Third Line of Defense is the immune response. Immune response targets specific antigens. Antigen any molecule that can be identified as foreign. May be a toxin (ie: bee sting), part of protein coating of virus, or molecule unique to plasma membranes of bacteria, pollen, etc. Major histocompatibility complex (MHC) mechanism by which immune system is able to differentiate between self and nonself cells. a collection of glycoproteins that exists on membranes of all body cells. extremely unlikely that any 2 people will have same set of these molecules. Lymphocytes WBCs that originate in the bone marrow but concentrate in lymphatic tissues like the lymph nodes, thymus gland, and spleen. 2 types: B cells and T cells. B cells lymphocytes that originate and mature in the bone marrow. they respond to antigens. the plasma membrane surface of B cells has special antibodies. Antibodies are antigen receptors, proteins, & specific to a partic antigen. has a "Y" shape. inactivates antigens by binding to them. Immunoglobulins 5 Classes: IgA, IgD, IgE, IgG, IgM. Each class has partic activity. Plasma B cells B cells that release their specific antibodies which then circulate through the body, binding to antigens. Memory B cells long-lived B cells that don't release their antibodies in response to the immediate antigen invasion. the cells circulate in body & respond quickly to eliminate any later invasion by the same antigen - this mech provs immunity to many diseases after the first occurrence of the disease. T cells lymphocytes that originate in the bone marrow, but mature in the thymus gland. have antigen receptors, but are recognition sites for molecules displayed by nonself cells (not antibodies). Cytotoxic T cells (aka killer T cells). recognize and destroy nonself cells by puncturing them, causing cell lysis. Helper T cells stimulate the proliferation of B cells and cytotoxic T cells. Clonal selection when an antigen binds to a B cell or when a nonself cell binds to a T cell, the B cell or T cell begins to divide, producing numerous daughter cells, all identical copies of the parent cell. *only the B or T cell bears the effective antigen receptor is "selected" and reproduces to make clones. cell-mediated response uses mostly T cells and responds to any nonself cell, including cells invaded by pathogens. 1) T cells produce cytotoxic T cells, 2) T cells produce helper T cells, 3) Helper T cells bind to macrophages, 4) Helper T cells produce interleukins to stimulate a proliferation of T cells and B cells. humoral response (antibody-mediated response). involves most cells and responds to antigens or pathogens that are circulating in the lymph or blood. 1) B cells produce plasma cells, 2) B cells produce memory cells, 3) Macrophage and helper T cells stimulate B cells production. Antibiotics chemicals derived from bacteria/fungi that are harmful to other microorganisms. Vaccines substances that stim the production of memory cells. Passive immunity obtained by transferring antibodies from an individual who previously had a disease to a newly infected individual. Newborns are protected by mother via placenta/breast milk. Clonal selection The process by which an antigen selectively binds to and activates only those lymphocytes bearing receptors specific for the antigen. The selected lymphocytes proliferate and differentiate into a clone of effector cells and a clone of memory cells specific for the stimulating antigen. cytokine Any of a group of small proteins secreted by a number of cell types(like macrophages), including macrophages and helper T cells, that regulate the function of other cells. effector cells 1) A muscle cell or gland cell that performs the body's response to stimuli as directed by signals from the brain or other processing center of the nervous system. (2) A lymphocyte that has undergone clonal selection and is capable of mediating an adaptive immune response. dendritic cells An antigen-presenting cell, located mainly in lymphatic tissues and skin, that is particularly efficient in presenting antigens to helper T cells, thereby initiating a primary immune response. epitope A small, accessible region of an antigen to which an antigen receptor or antibody binds; also called an antigenic determinant. heavy chain One of the two types of polypeptide chains that make up an antibody molecule and B cell receptor; consists of a variable region, which contributes to the antigen-binding site, and a constant region histamine A substance released by mast cells that causes blood vessels to dilate and become more permeable in inflammatory and allergic responses. humoral immune response The branch of adaptive immunity that involves the activation of B cells and that leads to the production of antibodies, which defend against bacteria and viruses in body fluids. passive immunity antibodies specific for a particular microbe are administered, conferring immediate but temporary protection active immunity can be aquired though vaccination, an inactive or weakened form of a pathogen is administered, inducing B and T cell responses and immunological memory. innate immunity A form of defense common to all animals that is active immediately upon exposure to pathogens and that is the same whether or not the pathogen has been encountered previously. mast cells A vertebrate body cell that produces histamine and other molecules that trigger inflammation in response to infection and in allergic reactions. monoclonal antibody Any of a preparation of antibodies that have been produced by a single clone of cultured cells and thus are all specific for the same epitope. neutrophils The most abundant type of white blood cell. are phagocytic and tend to self-destruct as they destroy foreign invaders, limiting their life span to a few days secondary immune response The adaptive immune response elicited on second or subsequent exposures to a particular antigen. The secondary immune response is more rapid, of greater magnitude, and of longer duration than the primary immune response. (2-7 days) thymus A small organ in the thoracic cavity of vertebrates where maturation of T cells is completed. some lymphocytes migrate from the bone marrow to the ______ to mature into T cells Tolll like receptor A membrane receptor on a phagocytic white blood cell that recognizes fragments of molecules common to a set of pathogens