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Glossary Acute-Phase Reactants. A diverse group of proteins that progressively increase in the plasma during the first hours to days following tissue injury. ADA (Adenosine Deaminase). An enzyme of the purine salvage pathway that catalyzes the irreversible deamination of adenosine and 2'-deoxy- adenosine. ADA Deficiency. An autosomal recessive form of severe combined im- munodeficiency disease in man. ADCC (Antibody-Dependent Cytotoxic Cells). Lymphocytes bearing Fc receptors that mediate a cellular cytotoxic reaction to target tissue with the aid of Fc-bound specific antibody. Allogeneic. Having cells that are antigenically distinct. Refers to intra . . . . species genetic vanat~ons. ALS (Anti-Lymphocyte Serum). A specially prepared serum containing Sources used to compile this glossary include the following: Blakiston's Gould Medical Dictionary, 3d ea., McGraw-Hill Book Co., New York, 1,828 pp., 1972. Immunology, I. Roitt, J. Brostoff, and D. Male, Cower Medical Publishing, London, 316 pp., 1985. International Dictionary of Medicine and Biology, vols. 1 and 2, John Wiley & Sons, New York, 3,200 pp., 1986. Advanced Immunology, D. Male, B. Champion, and A. Cooke, J. B. Lippincott Co., Phila- delphia, 222 pp., 1987. 217

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2 18 GLOSSARY antibodies against lymphocytes. Used especially to prevent rejection of transplanted organs. Amyloidosis. Deposition of amyloid in various organs or tissues. Amyloid is a family of nonrelated beta-pleated sheet proteins that share the char- acteristic of extracellular fibril deposition. ANA (Antinuclear Antibody). Any antibody capable of binding to com- ponents of the cell nucleus. Anemic. Characterized by a reduction of erythrocytes, hemoglobin, or hematocrit to below normal levels. Anterior Hypophysis. The anterior lobe of the pituitary gland. Anti-DNP (Anti-Dinitrophenol). An antibody directed toward dinitrophe- nol. Spontaneous elevations of this antibody in the plasma have been associated with some autoimmune phenomena. Anti-dsDNA (Anti-Double-Stranded DNA). An autoantibody frequently seen in patients with systemic lupus erythematosus and certain related connective tissue diseases. Anti-IFN (Anti-Interferon). Antibodies directed against interferon. Anti-SM (Anti-Smith). An autoantibody directed toward a nuclear antigen present in active chromatin. It is resistant to both deoxyribonuclease (DNase) and ribonuclease (RNase) and specific for the diagnosis of systemic lupus erythematosus. Anti-ssDNA (Anti-Single-Stranded DNA). An autoantibody frequently seen in the plasma of people afflicted with autoimmune disease. Ataxia Telangiectasia. An inherited disorder characterized by the onset of progressive cerebellar ataxia in infancy or childhood, oculocutaneous telangiectasia, frequent infections of the lungs and sinuses, and a propen- sity for the development of malignant disease. It is often associated with defects in cellular immunity and in the immunoglobulin system. Atrophy. An acquired physiologic or pathologic local reduction in the size of a cell, tissue, organ, or region of the body. Autoantibodies. Antibodies produced by a host to its own tissues. Autoimmune Disease. A disease involving a humoral or cell-mediated immune attack against the tissues of one's own body. Autoimmunity. A condition presumed to be caused by sensitization or loss of tolerance to autochthonous products of the body. A failure of the immune system to discriminate between self and nonself. B Cells. Lymphocytes that secrete antibody and that are characterized by the presence of certain surface membrane markers, that is, immunoglobulin receptors. Backcross. A cross between a hybrid and its parent or between a heter- ozygote and a homozygote.

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GLOSSARY 2 19 Balanced Stock. A genetic stock that is heterozygous for closely linked genes and produces phenotypically recognized offspring types. One off- spring type is used to produce the next generation and is of a predicted genotype unless crossing over has occurred between the linked loci. Barrier-Maintained Animals. Animals, usually defined-flora or patho- gen-free, placed in an environment that can serve as a barrier to the introduction of other microbes. Basophils. A circulating polymorphonuclear leukocyte that has a small number of prominent purple or black cytoplasmic granules when stained with Romanowsky dyes. The granules contain histamine and chondroitin sulfate. In tissues it is called a mast cell. BCGF-2 (B-Cell Growth Factor Type 2~. Isolated from murine T-cell cultures this 50- to 55-kilodalton glycoprotein drives activated B cells to maturation. BGG (Bovine Gamma-Globulin). serum of cattle. The gamma-globulin fraction from the C3bi. Inactivated form of the split product of the third component of com- plement, C3b. Calcitonin. A single-chain polypeptide hormone, apparently existing as several active fractions, secreted by the thyroid gland and the ultimobran- chial bodies. A calcitoninlike substance has also been extracted from por- cine adrenal glands. In hypercalcemia the hormone rapidly lowers blood calcium by inhibiting bone resorption; it also increases urinary excretion of phosphate. Called by some investigators thyrocalcitonin. Centromere. A small body at the constriction in a chromosome where it is attached to a spindle fiber. Chediak-Higashi Syndrome. A human syndrome (with homologous ge- netic disorders in many mammalian species) with deeply staining, coarse peroxidase-positive granules in the cytoplasm of neutrophils and eosino- phils. These granules are associated with albinism, hepatosplenomegaly, lymphadenopathy, and recurrent skin and pyogenic infections. When al- binism is absent, the condition is called the Steinbrinck type. See the beige (by) mutation of mice (p. 401. Chemotaxis. Increased directional migration of cells, particularly in re- sponse to concentration gradients of certain chemotactic factors. Chromosome. Intranuclear elements composed of DNA and protein that carry the hereditary factors (genes) and are present at a constant number . , . 1n eacn species. Class I MHC Antigens. Antigens encoded by the major histocompatibility complex (MHC) of genes that are found on all nucleated cells and are composed of two polypeptide chains of 45 and 12 kilodaltons.

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220 GLOSSARY Class II MHC Antigens. Also known as Ia antigens, they are found on antigen-presenting cells and are composed of two polypeptide chains of 28 and 32 kilodaltons. cM (Centimorgans). One one-hundreth of a Morgan. A measurement of length along the chromosome having a corrected crossover frequency of 1 percent. CMI (Cell-Mediated Immunity). A term used to refer to immune reactions that are mediated by cells rather than by antibody or other humoral factors. Codominant. Of or pertaining to two alleles that are both expressed in a heterozygote. The phenotype is the additive function of the two alleles. Coisogenic Strain. A congenic strain whose difference is limited to a single genetic locus. Complement. Any one of a group of at least nine factors, designated C1, C2, etc., that occur in the serum of normal animals and enter into various immunologic reactions. Complement is generally absorbed by combina- tions of antigen and antibody and, with the appropriate antibody, can lyse erythrocytes, kill or lyse bacteria, enhance phagocytosis and immune ad- herence, and exert other effects. Complement activity is destroyed by heating the serum at 56C for 30 minutes. ConA (Concanavalin A). A lectin produced by the jack bean that combines membrane glycoproteins containing alpha-glucoside or alpha-mannoside groups and serves as a mitogen for T cells. Congenic Strain. A strain that differs from the parental inbred strain at one restricted region of the genome. Contact Sensitivity. Also called contact hypersensitivity. An epidermal reaction characterized by eczema and caused when an antigen is applied to previously sensitized skin. Conventional Environment. Environmental conditions where the micro- bial flora are unknown and uncontrolled. Coombs' Positive Hemolytic Anemia. Anemia characterized by the at- tachment of anti-erythrocyte antibody and leading to sequestration of eryth- rocytes in the reticuloendothelial system or to complement-mediated intravascular hemolysis. CRI (Cross-Reactive Idiotype). An idiotype that can be detected on two different antibodies is termed a cross-reactive idiotope, and the antibodies that share them are cross-reactive idiotypes. Cyclosporine A. An immunosuppressive drug commonly used in organ transplantation. It appears to mediate its suppressive effect mainly through CD4+ (helper) T cells. Cytotoxic T Cell (Tc). A thymic-derived lymphocyte that circulates in search of a target cell displaying a determinant recognized by its receptor. It must recognize target cell antigen in association with class I major histocompatibility complex determinants.

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GLOSSARY 22 1 Defined-Flora. Animals that have a microbial flora that is completely known. Delayed-Type Hypersensitivity. A type IV immunologic reaction initiated by T lymphocytes and characterized by a delayed inflammatory response. Previous sensitization is required. Examples include response to Myco- bacterium tuberculosis (tuberculin test) and contact dermatitis (poison ivy). Dendritic Cells. Antigen-presenting cells present in lymph nodes, spleen, and at low levels in blood that are particularly active in stimulating T cells. DES (Diethylstilbestrol). A nonsteroid estrogen used as a substitute for the natural estrogenic hormones, it is more readily absorbed from the alimentary canal than most of the natural hormones and hence is suitable for oral use. Diabetes Mellitus. An inherited chronic disorder of carbohydrate metab- olism caused by a disturbance of the normal insulin mechanism and char- acterized by hyperglycemia, glycosuria, and alterations of protein and fat metabolism. It produces polyuria, polydipsia, weight loss, ketosis, aci- dosis, and coma. DNFB (2,4-Dinitro-l-Fluorobenzene). A chemical that, when applied top- ically to skin, sensitizes the host so that a second application causes contact . . . sensltlvlty. Dysgenesis. Abnormal development of anything, usually of an organ or individual. Impairment or loss of the ability to procreate. EAE (Experimental Allergic Encephalomyelitis). A disease state induced by the inoculation of allogeneic spinal cord that is characterized by in- flammation of the brain and spinal cord. Erythropoiesis. The differentiation and proliferation of erythrocytes. FACS (Fluorescence-Activated Cell Sorting). A procedure for mechan- ically separating cells based on the presence of membrane-bound fluores- cent dyes. Commonly, the dye is attached to a specific antibody, which directs it to a particular plasma membrane determinant. Fc Receptors. Membrane receptors in cells capable of binding the Fc portion of immunoglobulin molecules. FTS (Facteur Thymique Serique). A nine-amino-acid residue thymic hor- mone; also called thymulin. F Number. Indicates the number of filial or brother x sister generations. GA (Garlic Acid). 3,4,5-Trihydroxybenzoic acid, C7H6Os, formerly used internally as an astringent; esters of the acid are used as antioxidants. Gene. The biologic unit of heredity. It is self-reproducing and located at a specific location (locus) on a specific chromosome. Genotype. The genetic material inherited from parents; not all of it necessarily expressed in the individual (cf. phenotype).

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222 GLOSSARY Germfree Environment. An environment free of all known microbes. Germfree Isolator. An apparatus used to maintain animals in a germfree environment. GIF (Glucocorticoid Increasing Factor). A substance made by certain lymphocytes that exerts its stimulatory effect through the pituitary gland. Glomerulonephritis. An acute or chronic, usually bilateral, diffuse non- suppurative inflammatory kidney disease primarily affecting the glomeruli. It is characterized by proteinuria; cylindruria; hematuria; and often edema, hypertension, and nitrogen retention. Glucocorticoid. An adrenal cortex hormone that affects the metabolism of glucose. Any related natural or synthetic substance that functions sim- ilarly. In pharmacologic doses, these substances have immunosuppressive effects. Gnotobiotic. Germfree animals or germfree animals into which a defined microflora is introduced. The defined flora should be few in number and nonpathogenic. gp70 (GIycoprotein 70~. A 70,000-dalton c1Ycoorotein found on the en- velope of murine leukemia viruses. GM-CSF (Granulocyte-Macrophage Colony Stimulating Factor). A glycoprotein hormone that stimulates mveloir1 nro~.nitor oellc to nrorl~lr~ neutrophils, macrophages, and eosinophils. GVH (Graft-Versus-Host Reactions). An immunologic reaction charac . O ~ ' - - --J _ ~ _ _ = ~_ ~ ^ terlzed by donor (grafted) lymphocytes attacking host cells based on the recognition of histocompatibility antigens on host cells not present on the donor lymphocytes and the inability of host lymphocytes to reject the donor cells. Haplotype. A set of genetic determinants located on a single chromosome. Hashimoto's Thyroiditis. A chronic autoimmune disease of the thyroid, more common in women, that presents as thyroid gland enlargement and hypothyroidism. The gland is densely infiltrated with lvmnhonvte.s once is ultimately destroyed. Hematocrit. The percentage of the whole-blood volume occ~nier1 hv ~.rvth- rocytes after centrifugation. Hemizygous. ~1 ~r - _ _ J _ _ _< _ _ _ _ J ~ _ J _~ J _^A the presence of only one of a pair of genes that influence one cleterm~nat~on or a specific trait. For example, a male has few alleles on his Y chromosome; therefore, most of the alleles on his X chromosome are expressed whether they are dominant or recessive. Henoch-Schonlein Purpura. A disease, primarily of young children, con- sisting of small-vessel vasculitis seen as raised red spots on the skin, glomerulonephritis, abdominal pain, fever, and arthritis. It is thought to be a form of allergic vasculitis.

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GLOSSARY 223 HEPA (High-Eff~ciency Particulate Air Filter). A filter capable of re- taining 99.97 percent of a 0.3-~m diameter monodispersed aerosol. Heterozygosity. Having dissimilar alleles in one or more pairs of gene loci. Heterozygote. An individual that has different alleles in the corresponding loci of homologous chromosomes and does not breed true. HGG (Human Gamma-Globulin). The gamma-globulin fraction of hu- man serum. An extract of serum from hyperimmune humans that is used as passive immunotherapy in patients exposed to an infectious disease, for example, rabies immune globulin. Histamine. 4-~2-Aminoethyl)-imidazole, C5H,N3, an amine occurring as a decomposition product of histidine that stimulates visceral muscles; di- lates capillaries; and stimulates salivary, pancreatic, and gastric secretions. It is found in the granules of the basophils and mast cells responsible for anaphylactic reactions. Holandric Inheritance. Transmission of a trait via the male lineage; trans- mitted through genes on the Y chromosome. Homozygote. An individual that has identical alleles in the corresponding loci of homologous chromosomes and breeds true. Hybrid. The offspring of a cross between two inbred strains. Hypergammaglobulinemia. The increased concentration of immunoglob- ulins in the blood seen in a wide variety of clinical disorders. Hyperplasia. Excessive fo~ation of tissue; an increase in the size of a tissue or organ caused by an increase in the number of cells. Ia-Associated Antigen. A surface antigen of mouse cells, such as B lym- phocytes and macrophages, that is determined by the I-A region of the major histocompatibility complex. Idiotope. A single antigenic determinant on an antibody V region. Idiotype. The antigenic characteristic of the V region of an antibody. IL-I (Interleukin-1~. An acute-phase reactant synthesized by many cell types, including monocytes and lymphocytes. This hormone has many effects, including the activation of resting T cells, the promotion of syn- thesis of other lymphokines, and the activation of macrophages and en dothelial cells. IL-2 (Interleukin-2~. A growth factor for activated T cells, this hormone is derived from lymphocytes and promotes the synthesis of other lym phokines. IL-3 (Interleukin-3~. A multilineage colony stimulating factor released by T cells that appears to act synergistically with granulocyte-macrophage colony stimulating factor to stimulate hematopoiesis. It is also a growth factor for mast cells.

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224 GLOSSARY IL-4 (Interleukin-4~. Also known as B-cell stimulating factor type l, this is a growth factor for B cells and induces class II major histocompatibility complex antigen expression on their surfaces. This hormone also enhances the cytolytic activity of cytotoxic T cells and is a mast cell growth factor. IL-6 (Interleukin-64. Also known as B-cell stimulating factor type 2 or B-cell differentiation factor, it induces the differentiation of activated B cells into immunoglobulin-secreting plasma cells. Immune Complex. The product of an antigen-antibody reaction that can also contain components of the complement system. Immunodeficiency. The inability of the host to eliminate or neutralize foreign substances. Immunologic Memory. A phenomenon characterized by the presence in the body of an expanded set of clonally derived antigen-specific lympho- cytes that can be rapidly recruited to produce an augmented immune re- sponse on subsequent exposure to the specific antigen. Immunoglobulins. Proteins of animal origin with known antibody activity or a protein related by chemical structure and hence antigenic specificity. They can be found in plasma, urine, spinal fluid, and other body tissues and fluids and include such proteins as myeloma and Bence Jones protein. Inbreed. To mate brother x sister each generation. Inbred Strain. A strain produced by at least 20 generations of brother x sister inbreeding. Incisor Teeth. The two cutting teeth nearest the midline in each quadrant of the dentition. Also called dentes incisive. Intercrossing. The mating of diploid individuals who are both heterozy- gous for one or more of the same alleles at given loci. Interferons. Proteins that are formed by animal cells in the presence of a virus, that prevent viral reproduction, and that are capable of inducing resistance to a variety of viruses in fresh cells of the same animal species. There are three classes: alpha, beta, and gamma. Alpha interferon (IFNa) is made by lymphocytes and macrophages and is 18-20 kilodaltons in size. Beta interferon (IFNQ) is synthesized by fibroblasts and epithelial cells. Alpha and beta interferons were once called type 1 interferon. Gamma interferon (IFNy), also called type 2 interferon, is synthesized by lym- phocytes. All three interferons can be induced during viral infection. They have antiviral and antiproliferative effects, and all induce class I major histocompatibility complex antigens. Islets of Langerhans. Islets of the pancreas containing hormone-producing cells: beta cells produce insulin; alpha cells produce glucagon. Isotypes. Genetic variation within a family of proteins or peptides such that every member of a species has each isotype of the family represented in its genome (e.g., immunoglobulin classes).

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GLOSSARY 225 Kappa ('c) Chain. One of the immunoglobulin light-chain isotypes. Ketosis. A condition in which ketones are present in the body in excessive amounts. The acidosis of diabetes mellitus. Lambda (A) Chain. One of the immunoglobulin light-chain isotypes. Laminar Flow. Air flow characterized by the absence of turbulence. Langerhans' Cells. Stellate cells of the mammalian epidermis and clerks presumed to belong to the melanocyte series, revealed by gold ~mpreg- nation, and containing nonmelanized disklike organelles. They are antigen- presenting cells that emigrate to the local lymph nodes to become dendritic cells. They are particularly active at presenting antigen to T cells. Lentivirus. One member of the virus family Retroviridae. Many species . have the ability to infect animals, including man, and have long incubation periods. These viruses usually are not oncogenic. Linked Genes. In eukaryotic cells, genes are said to be linked if they are carried on the same chromosome, that is, do not segregate randomly. Lipid A. The endotoxic component of lipopolysaccharide. LPS (Lipopolysaccharide). A compound of a lipid with a polysaccharide. A component of gram-negative bacteria that is liberated on bacterial death and might be responsible for shock; also called endotoxin. Lymphadenopathy. Lymph node enlargement. Lymphoblasts. A blast cell, considered a precursor or early form of a lymphocyte. Lymphocyte Activating Factor. Lymphokines. A generic term for molecules other than antibodies that are involved in signaling between cells of the immune system and are produced by lymphocytes (cf. interleukins). Lymphomas. Any neoplasm, usually malignant, of the lymphatic tissues. Lymphopenia. Lymphocytopenia. A reduction in the number of circulating lymphocytes. Lymphopoietic. Also called interleukin-l. Lymphocytopoiesis. Production of lymphocytes. Macrophages. derived from defense mechanisms. A phagocytic cell that is found in many tissues, that is a blood monocyte, and that has an important role in host MALT (Mucosal-Associated Lymphoid Tissue). Generic term for lym phoid tissue associated with the mucosa of the gastrointestinal tract, bron chial tree, urinary tract, and other systems. Mast Cell. A small cell similar in appearance to a basophil and found associated with mucosal epithelial cells. These cells are dependent on T cells for proliferation, and they contain cytoplasmic granules laiden with heparin, slow reactive substance of anaphylaxis, and eosinophil chemo

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226 GLOSSARY tactic factor of anaphylaxis, which are released when antigen binds to membrane-bound IgE. Melanocyte. The epidermal cell that synthesizes melanin. Membrane Attack Complex. A multimolecular complex formed by the activation of the terminal components of the complement pathway and responsible for cytolysis. MHC (Major Histocompatibility Complex). A genetic region found in all mammals whose products are primarily responsible for the rapid re- jection of grafts between individuals and that function in signaling between lymphocytes and cells expressing antigen. ~,, _ _ ~ ~ O -- ~ MHV (Mouse Hepatitis Virus). A single-stranded RNA virus of the family Coronaviridae, genus Coronavirus. MHV infections are usually subclinical in immunocompetent mice but can cause severe illness and death in im- munodeficient mice. Mitogens. Substances that cause cells, particularly lymphocytes, to un- dergo cell division. MLC (Mixed Lymphocyte Culture). The proliferative assay system for T-cell recognition of foreign antigen on allogeneic cells, in which response is measured by DNA synthesis (intercollation of radiolabeled nucleic acid). MLR (Mixed Lymphocyte Reaction). See MLC. Monoclonal Antibodies. Antibodies arising from a single clone of B lym- phocytes. MuLV (Murine Leukemia Virus). An RNA virus of the family Retro- viridae. An endogenous virus of mice that causes leukemias and related malignancies in some mouse strains. Strain susceptibility is influenced by a number of genes, including Fv-l, Fv-2, In, nu, hr. and Ir. Mutations. A change in the characteristics of an organism produced by an alteration in the hereditary material. The alteration in the ~ermnlasm might involve an addition of one or more complete sets of chromosomes; the addition or loss of a whole chromosome; or some change within a chro- mosome, ranging from a gross rearrangement, loss, or addition of a larger or smaller section to a minute rearrangement or change at a single locus. A small change at a single locus is called a gene mutation or, more simply, mutation in the restricted use of the term. Myelopoiesis. The process of formation and development of blood cells in the bone marrow. ~r D N. Indicates the number of backcrosses made to an inbred strain. Necrosis. The pathologic death of a cell or group of cells. NK (Natural Killer) Cells. A group of lymphocytes with the intrinsic ability to recognize and destroy some virally infected cells and some tumor cells. Nephritogenic. Giving rise to inflammation of the kidney.

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GLOSSARY 227 NTAs (Natural Thymocytotoxic Antibodies). Autoantibodies directed against determinants present on thymic-derived lymphocytes, as defined by complement-dependent lysis of target thymocytes. Oncornavirus. Any of the various tumor-producing viruses of the family Retroviridae. Also called oncovirus. Osteoclast. A multinuclear giant cell responsible for bone absorption and destruction. Ovarian Transplantation. A technique of placing a compatible ovary in the ovarian capsule (from which the original ovary has been removed) of a selected host. Osteopetrosis. A heterogeneous group of hereditary disorders that share generalized sclerosis and fragility of the skeleton and elevated serum acid phosphatase. Osteosclerosis. An abnormal thickening of bone. P-1SE. A transmembrane portion of the envelope of certain oncoviruses thought to be responsible for viral-associated immunosuppression. Parabiosis. The experimental surgical fusing together of two individuals or embryos so that the effects of one partner on the other can be studied. Parathyroid Hormone. A polypeptide hormone in parathyroid glands that regulates blood calcium levels. Pathogen-Free Environment. An environment free of all known patho- genic microorganisms, tested pathogens, or both. PBB (Polybrominated Biphenyl). Any of a series of stable compounds in which the hydrogen atoms in biphenyls are replaced by bromine. These, along with polychlorinated bichenvls. are serious toxic pollutants in the environment. ~, PBLs (Peripheral Blood Lymphocytes). in blood. Penetrance. Circulating lymphocytes found The percentage of organisms with a given genetic constitution that show the corresponding hereditary characteristic. Peyer's Patches. Specialized lymphoid tissue found in the intestinal tract. PFC (Plaque-Forming Cell). An antibody-secreting B cell that can be recognized by the production of a hemolytic plaque. PG (Propylgallate). 3,4,5-Trihydroxybenzoic acid propyl ester, an an- tioxidant. PHA (Phytohemagglutinin). A lectin isolated from red kidney beans that is mitogenic for T cells. Phagocytosis. Ingestion of foreign or other particles by certain cells. Phenotype. The expressed characteristics of an individual (cf. genotype). Pleiotropic. The occurrence of multiple effects produced by a given gene.

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228 GLOSSARY PMN (Polymorphonuclear Leukocyte). The mature neutrophil leukocyte, so-called because of its segmented and irregularly shaped nucleus. Pneumonitis. Inflammation of the lungs in which the exudate and inflam- matory cell incursion is primarily interstitial. Poly(A-U) (Polyadenylic-Polyuridylic Acid). A synthetic RNA polymer. Polyarteritis Nodosa. A systemic disease characterized by widespread in- flammation of small- and medium-sized arteries in which some of the foci are nodular. Complications of the process, such as thrombosis, lead to retrogressive changes in the tissues and organs supplied by the affected vessels with a correspondingly diverse array of symptoms and signs. It is also called periarteritis nodosa or disseminated necrotizing periarteritis. Poly (I-C). One of the synthetic RNA polymers that induce the local pro- duction of interferon. It has been used experimentally in the topical treat- ment of acute herpesvirus infection of the cornea. Prokaryotic. Pertaining to a unicellular organism that has a single chro- mosome, lacks a nuclear membrane, and usually has a rigid peptidoglycan wall. PGE2 (Prostaglandin E21. An unsaturated fatty acid 20 carbons in length with an internal cyclopentane ring. It causes vasodilatation, inhibits gastric secretion, induces labor and abortion, and is immunosuppressive. A de- rivative of arachidonic acid. Protein A. A cell wall component of certain strains of staphylococci that binds to a site in the Fc region of most IgG isotypes. PWM (Pokeweed Mitogen). A mitogen for B cells. RCS (Reticulum-Cell Sarcomas). A malignant tumor in which the pre- dominant cell type is an anaplastic reticulum cell. Multinucleated cells also occur. Also called histiocytic sarcoma. Recombinant Inbred. A strain formed by crossing two inbred strains, followed by 20 or more generations of brother x sister mating. Reed-Sternberg Cell. A large binucleated or multinucleated cell, 15-45 ~m in diameter, that is derived from the reticuloendothelial system. It is a distinctive giant cell found in all Hodgkins' lymphomas. Repulsion. The occurrence of two linked loci, each in the heterozygous state, with the mutant alleles on different homologous chromosomes. RES (Reticuloendothelial System). A diffuse system of phagocytic cells, many of which are derived from bone marrow stem cells. It is associated with the connective tissue framework of the liver, spleen, lymph nodes, and other serous cavities. The site of renewal for endothelial cells is thought to be existing endothelial cells rather than bone marrow. Retroviral. Relating to retroviruses, RNA viruses belonging to the family Retroviridae that are characterized by the presence of a reverse transcriptase (RNA-dependent ONA polymerase) enzyme.

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GLOSSARY 229 RFs (Rheumatoid Factors). A group of autoantibodies that are directed against the Fc fragment of the heavy chain of IgG. RFLP (Restriction Fragment Length Polymorphism). DNA fragments of various sizes resulting from the action of endonucleases cleaving DNA at specific sites (restriction enzymes). Semidominant. Incomplete dominance. Serotonin. 5-Hydroxytryptamine, CloHl2N2o, which is present in many tissues, especially blood and nervous tissue. It stimulates a variety of smooth muscles and nerves and is postulated to function as a neurotrans- mitter. Serum Alkaline Phosphatase. Serum levels of a specific phosphatase en- zyme found in various tissues. Elevation of this enzyme in the serum usually indicates hepatobiliary disease in mammals. SAA (Serum Precursor Amyloid). An alpha-globulin that displays acute- phase increases and is believed to be the precursor of the amyloid A fibrils present in secondary amyloidosis. SDS Gel Electrophoresis. A form of polyacrylamide gel electrophoresis conducted with sodium dodecyl sulfate (SDS) in the buffer. SPF (Specific-Pathogen-Free). Free of specifically defined pathogenic mi- croorganisms. Splenomegaly. Increased spleen size; it is seen in a number of parasitic infections, hemolytic anemias, and lymphomas and is also measured in the Simonson assay for graft-versus-host reactions. SRBC (Sheep Red Blood Cell). A T-cell-dependent target antigen often used in hemolytic plaque assays of immune responsiveness. Stem Cell. Pluripotent cells that can serve as progenitor cells for the lym- phoid lineage or the myeloid lineage or both (hemopoietic stem cell). SV40 (Simian Virus 40~. A papovavirus commonly seen in tissues of Old World monkeys without being associated with disease. Synergistic. An agent that increases the action or effectiveness of another agent when combined with it. Syugeneic. Individuals or tissues that have identical genotypes, for ex- ample, animals of the same inbred strain. SLE (Systemic Lupus Erythematosus). An autoimmune disease of hu- mans usually involving antinuclear antibodies and characterized by skin rash, hematologic alterations, and glomerulonephritis. TCDD (Tetrachlorodibenzo-p-Dioxin). One member of a group com- monly referred to as dioxins that is widespread in the environment and is . . 1mmunosuppresslve. T-Cell- or Thymic-Derived Lymphocytes. One of the two major classes of lymphocytes with important immune regulatory and effector functions.

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230 GLOSSARY T cells must pass through the thymus during development, and they carry certain characteristic surface markers such as theta and the CD3 antigens. Tdt (Terminal Deoxyoucleotidyl Transferase). An enzyme present in pre-T or thymic stem cells. It is present in cortical but lost in medullary and peripheral cells. Th Cell or Helper T Lymphocyte. A functional subclass of T cells that can help generate cytotoxic T cells and cooperate with B cells in the production of an antibody response. Helper T cells usually recognize an- tigen in association with class II major histocompatibility complex mol- ecules. Currently defined using CD4 markers. Thymulin. An 867-dalton peptide isolated from thymus and serum that appears to be responsible for T-cell differentiation. Also known as facteur thymique serique (FTS). Thymus. An organ found in the thoracic or cervical regions of mammals that is composed of lymphatic tissue in which minute concentric bodies, the remnants of epithelial structures, or thymic corpuscles are found. This organ is necessary for the development of thymic-derived lymphocytes and is the source of several hormones involved in T-cell maturation, for example, thymosin, thymopoietin, thymulin, and thymocyte humoral fac- tor. Thymus-Dependent Antigen. An antigen that requires an immune re- sponse from thymic-derived lymphocytes in order to elicit an immune response from B lymphocytes. Thymus-Independent Antigen. An antigen that does not require the par- ticipation of T lymphocytes to elicit an immune response in B cells. Ti or TCR (T-Cell Antigen Receptor). The antigen receptor of T cells composed of two polypeptide chains and closely associated with the T3 surface membrane molecules. TLI (Total Lymphoid Irradiation). X-irradiation directed toward lym- phoid organs throughout the body. Tolerance. A state of specific immunologic unresponsiveness. Ts Cell or Suppressor T Lymphocyte. A subpopulationfs) of T cells that acts to reduce the immune responses of other T or B cells. Suppression can be antigen specific, idiotype specific, or nonspecific under different circumstances. At present, cells with this function cannot be identified using one marker, although many appear to carry the CD8 molecule. Type 1 Antigens. T-cell-independent (TI) antigens that can stimulate both Lyb-5 + and Lyb-5 - B cells in the mouse. TI type 2 antigens only stimulate Lyb-S+ B cells. UVR (Ultraviolet Radiation). Radiation with a wavelength shorter than that of the violet end of the visible spectrum and longer than that of x rays

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GLOSSARY 231 (from 180 to 390 nary). Exposure to UVR can be associated with tissue damage, malignant transformation, or immunosuppression. Vibrissae. One of the hairs in the vestibule of the nose. One of the long, coarse hairs on the face of certain animals; "whiskers." Viral-Antibody-Free. Free of circulating anti-viral antibodies to specific viruses, usually pathogenic viruses. Vitiligo. A condition of the skin characterized by a failure to form melanin, with patches of depigmentation that often have a hyperpigmented border and enlarge slowly. Wild Type. Of or relating to a genetic locus or an allele that specifies a phenotype that predominates in natural populations or that is designated as normal. Xenografts. A transplant from one species to another; sometimes used to indicate a wider genetic or species disparity than in a heterograft.

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