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| 9876553462 | pathogen | an organism or virus that causes disease | 0 | |
| 9876553463 | immune system | an animal body's system of defenses against agents that cause disease | 1 | |
| 9876553464 | 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 | 2 | |
| 9876553465 | adaptive immunity | a vertebrate-specific defense that is mediated by B lymphocytes (B cells) and T lymphocytes (T cells) and that exhibits specificity, memory, and self-nonself recognition; also called acquired immunity | 3 | |
| 9876553466 | lysozyme | an enzyme that destroys bacterial cell walls; in mammals, found in sweat, tears, and saliva |  | 4 |
| 9876553467 | phagocytosis | a type of endocytosis in which large particulate substances or small organisms are taken up by a cell. It is carried out by some protists and by certain immune cells of animals (in mammals, mainly macrophages, neutrophils, and dendritic cells) |  | 5 |
| 9876553468 | toll-like receptor (TLR) | a membrane receptor on a phagocytic white blood cell that recognizes fragments of molecules common to a set of pathogens | 6 | |
| 9876553469 | neutrophil | the most abundant type of white blood cell. Neutrophils are phagocytic and tend to self-destruct as they destroy foreign invaders, limiting their life span to a few days |  | 7 |
| 9876553470 | macrophage | a phagocytic cell present in many tissues that functions in innate immunity by destroying microbes and in acquired immunity as an antigen-presenting cell | 8 | |
| 9876553471 | natural killer cell | a type of white blood cell that can kill tumor cells and virus-infected cells as part of innate immunity |  | 9 |
| 9876553472 | interferon | a protein that has antiviral or immune regulatory functions. Interferon-alpha and interferon-beta, secreted by virus-infected cells, help nearby cells resist viral infection; interferon-gamma, secreted by T cells, helps activate macrophages | 10 | |
| 9876553473 | complement system | a group of about 30 blood proteins that may amplify the inflammatory response, enhance phagocytosis, or directly lyse extracellular pathogens | 11 | |
| 9876553474 | inflammatory response | an innate immune defense triggered by physical injury or infection of tissue involving the release of substances that promote swelling, enhance the infiltration of white blood cells, and aid in tissue repair and destruction of invading pathogens | 12 | |
| 9876553475 | histamine | a substance released by mast cells that causes blood vessels to dilate and become more permeable in inflammatory and allergic responses |  | 13 |
| 9876553476 | mast cell | a vertebrate body cell that produces histamine and other molecules that trigger inflammation in response to infection and in allergic reactions | 14 | |
| 9876553477 | cytokine | any of a group of small proteins secreted by a number of cell types, including macrophages and helper T cells, that regulate the function of other cells | 15 | |
| 9876553478 | lymphocyte | a type of white blood cell that mediates immune responses. The two main classes are B cells and T cells | 16 | |
| 9876553479 | thymus | a small organ in the thoracic cavity o vertebrates where maturation of T cells is completed |  | 17 |
| 9876553480 | T cells | the class of lymphocytes that mature in the thymus; they include both effector cells for the cell-mediated immune response and helper cells required for both branches of adaptive immunity |  | 18 |
| 9876553481 | B cells | the lymphocytes that complete their development in the bone marrow and become effector cells for the humoral immune response | 19 | |
| 9876553482 | antigen | a substance that elicits an immune response by binding to receptors of B cells, antibodies or T cells | 20 | |
| 9876553483 | antigen receptor | the general term for a surface protein, located on B cells and T cells, that binds to antigens, initiating adaptive immune responses. The antigen receptors on B cells are called B cell receptors, and the antigen receptors on T cells are called T cell receptors | 21 | |
| 9876553484 | epitope | a small, accessible region of an antigen to which an antigen receptor or antibody binds; also called an antigenic determinant |  | 22 |
| 9876553485 | 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 | 23 | |
| 9876553486 | light 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 | 24 | |
| 9876553487 | antibody | a protein secreted by plasma cells (differentiated B cells) that binds to a particular antigen; also called immunoglobulin. All antibodies have the same Y-shaped structure and in their monomer form consist of two identical heavy chains and two identical light chains | 25 | |
| 9876553488 | major histocompatibility complex (MHC) molecule | a host protein that functions in antigen resentation. Foreign MHC molecules on transplanted tissue can trigger T cell responses that may lead to rejection of the transplant | 26 | |
| 9876553489 | antigen presentation | the process by which an MHC molecule binds to a fragment of an intracellular protein antigen and carries it to the cell surface, where it is displayed and can be recognized by a T cell | 27 | |
| 9876553490 | effector cell | a lymphocyte that has undergone clonal selection and is capable of mediating an adaptive immune response | 28 | |
| 9876553491 | plasma cell | the antibody-secreting effector cell of humoral immunity. Plasma cells arise from antigen-stimulated B cells | 29 | |
| 9876553492 | memory cell | one of a clone of long-lived lymphocyes, formed during the primary immune response, that remains in a lymphoid organ until activated by exposure to the same antigen that triggered its formation. Activated memory cells mount the secondary immune response | 30 | |
| 9876553493 | 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 | 31 | |
| 9876553494 | primary immune response | the initial adaptive immune response to an antigen, which appears after a lag of about 10-17 days | 32 | |
| 9876553495 | 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 | 33 | |
| 9876553496 | 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 | 34 | |
| 9876553497 | cell-mediated immune response | the branch of adaptive immunity that involves the activation of cytotoxic T cells, which defend against infected cells | 35 | |
| 9876553498 | helper T cell | a type of T cell that, when activated, secretes cytokines that promote the response of B cells (humoral response) and cytotoxic T cells (cell-mediated response) to antigens | 36 | |
| 9876553499 | antigen-presenting cell | a cell that upon ingesting pathogens or internalizing pathogen proteins generates peptide fragments that are bound by class II MHC molecules and subsequently displayed on the cell surface to T cells. Macrophages, dendritic cells, and B cells are the primary antigen-presenting cells | 37 | |
| 9876553500 | cytotoxic T cell | a type of lymphocyte that, when activated, kills infected cells as well as certain cancer cells and transplanted cells | 38 | |
| 9876553501 | active immunity | long-lasting immunity conferred by the action of B cells and T cells and the resulting B and T memory cells specific for a pathogen. Active immunity can develop as a result of natural infection or immunization | 39 | |
| 9876553502 | passive immunity | short-term immunity conferred by the transfer of antibodies, as occurs in the transfer of maternal antibodies to a fetus or nursing infant | 40 | |
| 9876553503 | immunization | the process of generating a state of immunity by artificial means. In active immunization, also called vaccination, an inactive or weakened form of a pathogen is administered, inducing B and T cell responses and immunological memory. In passive immunization, antibodies specific for a particular microbe are administered, conferring immediate but temporary protection |  | 41 |
| 9876553504 | 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 | 42 | |
| 9876553505 | allergen | an antigen that triggers an exaggerated immune response |  | 43 |
| 9876553506 | autoimmune disease | an immunological disorder in which the immune system turns against self | 44 | |
| 9876553507 | human immunodeficiency virus (HIV) | the infectious agent that causes AIDS. HIV is a retrovirus | 45 |
