Chapter 1 Definitions and Learning Objectives Define the following terms: Immune system – The molecules, cells, tissues, andorgans that collectively function to provide immunity,or protection, against foreign organisms.Immune response - collective and coordinatedresponse to the introduction of foreign substances or self molecules ( autoimmune response)Immunology – Study of immune responses against PathogensInnate immunity - Protection against infection thatrelies on mechanisms that exist before infection, arecapable of a rapid response to microbes, and react inessentially the same way to repeated infections. Theinnate immune system includes epithelial barriers,phagocytic cells (neutrophils, macrophages), NK cells,the complement system, and cytokines, largely madeby dendritic cells and mononuclear phagocytes, thatregulate and coordinate many activities of the cells ofinnate immunity.Adaptive immunity - The form of immunity that is mediatedby lymphocytes and stimulated by exposure toinfectious agents. In contrast to innate immunity, adaptiveimmunity is characterized by exquisite specificityfor distinct macromolecules and by memory, whichis the ability to respond more vigorously to repeatedexposure to the same microbe. Adaptive immunity isalso called specific immunity or acquired immunity.Antigen - A molecule that binds to an antibody or a TCR.Antigens that bind to antibodies include all classes ofmolecules. Most TCRs bind only peptide fragments ofproteins complexed with MHC molecules; both thepeptide ligand and the native protein from which it isderived are called T cell antigens.Antibody Cytokine - Proteins that are produced and secreted by many different cell types, and mediate inflammatory and immune reactions. Cytokines are principal mediators of communication between cells of the immune systemChemokine – A large family of structurally homologous low–molecular-weight cytokines that stimulate leukocyte chemotaxis, regulate the migration of leukocytes from the blood to tissues by activating leukocyte integrins, andmaintain the spatial organization of different subsets of lymphocytes and antigen-presenting cells within lymphoid organsCluster of differentiation (CD) – Cell surface molecules expressed on various cell types in the immune system that are designated by the “cluster of differentiation” or CD number. See Appendix III for a list of CD molecules.Inflammation – A complex reaction of vascularized tissue to infection or cell injury that involves extravascular accumulation of plasma proteins and leukocytes. Acute inflammation is a common result of innate immune responses, and local adaptive immune responses can also promote inflammation. Although inflammation serves a protective function in controlling infections and promoting tissue repair, it can also cause tissue damage and diseaseImmunologic memory - The property of the adaptive immune system to respondmore rapidly, with greater magnitude, and more effectively to a repeated exposure to an antigen compared with the response to the first exposureChapter 2 Granulocyte – cell with a granule Agranulocyte - no granulePhagocyte – cell in which can preform phagocytosisPhagocytosis - The process by which certain cells of the innate immune system,including macrophages and neutrophils, engulf large particles (>0.5 μm in diameter) such as intact microbes. The cell surrounds the particle with extensions of its plasma membrane by an energy- and cytoskeleton-dependent process; this process results in the formation of an intracellular vesicle called a phagosome, which contains the ingested particle.Cytokines – Proteins that are produced and secreted by many different cell types, and mediate inflammatory and immune reactions. Cytokines are principalmediators of communication between cells of the immune system Tissue resident cell (ie. macrophage) – A tissue-based phagocytic cell derived from fetal hematopoietic organs or blood monocytes that plays important roles in innate and adaptive immune responses. Macrophages are activated by microbial products such as endotoxin and by T cell cytokines such as IFN-γ. Activated macrophages phagocytose and kill microorganisms, secrete proinflammatory cytokines, and present antigens to helper T cells. Macrophages may assume different morphologic forms in different tissues, including the microglia of the central nervous system, Kupffer cells in the liver, alveolar macrophages in the lung, and osteoclasts in bone.Antigen presenting cell - A cell that displays peptide fragments of protein antigens, in association with MHC molecules, on its surface and activates antigen specific T cells. In addition to displaying peptide-MHC complexes, APCsalso express costimulatory molecules to optimally activate T lymphocytes(Classical) dendritic cell - Bone marrow–derived cells found in epithelial and lymphoid tissues that are morphologically characterized by thin membranous projections. Many subsets of dendritic cells exist with diverse functions. Classical dendritic cells function as innate sentinel cells and become APCs for naive T lymphocytes upon activation, and they are important for initiation of adaptive immune responses to protein antigen. Immature (resting) classical dendritic cells are important for induction of tolerance to self antigens. Plasmacytoid dendritic cells produce abundant type 1 interferons in response toexposure to viruses.Mature lymphocyte – Naive lymphocyte – Effector lymphocyte – Memory lymphocyte – Homeostatic proliferation – Pluripotent – CFU – CSF –Thymocytes – Hassall’s corpuscle – Thymic epithelial cell – Cortical epithelial cell – Lymph – Draining lymph node