I M M U N O G L O S S A R Y

 

Abzymes - immunoglobulins with catalytic activity.
Accidental involution - phenomenon of age-related atrophy of thymus. Accelerated by stresses, delayed in status thymico-lymphaticus.
Acquired immunodeficiency syndrome (AIDS) - HIV-infection in 3rd final crisis stage with bright manifestations, both laboratory ( CD4+ cell number in peripheral blood less than 200/ m L) and clinical (indicator opportunistic infections, neurological and neoplastic disorders).
Active immunization - induction of immune defenses by the administration of vaccines and toxoids.
Adoptive transfer - the translocation of the ability for DTH towards a given allergen from sensitized donor to non-sensitized recipient via donor's whole blood, or T lymphocytes (for example with bone marrow transplantation), a kind of passive immunization
AIDS-related complex (ARC) - the symptomocomplex, which develops in many patients in second chronic phase of HIV-infection and is characterized by long-lasting fever (3 months or longer) that may be intermittent or continuous, weight loss, and diarrhea. ARC patients are clearly symptomatic, but have no indicator opportunistic and neoplastic diseases of AIDS, obligatory for bright final manifestation of HIV-infection.
Allergens - antigens when they are regarded as a cause of allergy.
Allergic breakthrough - triggering of anaphylactic reaction by means of some complex of non-specific factors, increasing general reagin production and decreasing suppressive mechanisms to trespass the threshold of allergy.
Allergization - (syn. - sensitization) excessive and/or poorly regulated primary immune response.
Allergoid - in some clinical texts - chemically modified allergen.
Allergoid (allergy-like) reactions - reactions which have the clinical manifestations very close to that of allergic reactions, but do not depend on antibodies or sensitized lymphocytes. Term is of no relation to another meaning of allergoid (see above).
Allergy also called in many American texts "Hypersensitivity" - collective term, designating the group of various typical immunopathological processes, which develop in sensitized organism of genetically predisposed individuals during boosted immune response for the antigen, earlier provoked sensitization. Every one of these processes, in spite of difference in their mechanisms, as a rule, is manifested in hyperergic inflammation.
Allotypes - The variants of heavy chains antigenic structure, determined by allele polymorphism of appropriate genes and characteristic for somatotype of certain groups of individuals.
Amyloid - group of pathologic proteinaceous substances, similar in mode of their regular structure, in stained slices it appears as pink translucent material deposited between cells in various tissues and organs of the body, in a wide variety of clinical settings (amyloidosis).
Anamnestic response - non-specific increase triggered by any antigen in immunogenesis against different ones due to universal production of immunostimulant cytokines.
Anaphylaxis - 1st category of ITH, local or systemic immunopathological reactions, mediated by reagins and allergen-reagin dependent degranulation of mastocytes, basophils, eosinophils and some other cells.
Anaphylotoxins - The complement fragments (C5a, C3a, C4a) capable to elicit the local mast cell and basophil degranulation and vascular permeability increase, thus promoting edema and chemotaxis of polymorphonuclear leukocytes.
Antibody - (syn. Immunoglobulin) Plasma cell and B lymphocyte product, the main effector of specific humoral immunity, consisting of heavy and light chains and complementary to certain antigen.
Antibody-dependent cellular cytotoxicity - targeted lysis of the cells without their engulfment by immunoglobulin-mediated attachment of K-cells.
Antigen - biological polymer molecule capable of eliciting immune response through association to specific T and B receptor.
Antigenicity - the property of biopolymers and their complexes to be specifically recognized and memorized by immune system.
Antigen-presenting cells - system of mononuclear phagocytes and some closely related kinds of cells (glial, Langerhans', dendritic and thymic stellate cells) which, basically, perform the function of the antigen-presentation and antigen processing for lymphocytes.
Anti-idiotypic antibodies - immunoglobulins towards the antigenic determinants on the V domains of antibodies. If the anti-idiotypic antibody is directed precisely against the antigen-combining site (paratope) of the original antibody, the configuration of its own V-region will resemble the antigen (epitope) itself (Ab2b ), although anti-idiotypes directed against idiotopes irrelevant to paratope also may exist, and they do not resemble epitope (Ab2a ).
Apoptosis - a kind of programmed cellular self-disassembly, with minimal possible dissipation of inflammation mediators.
Arthus' phenomenon - local immune complex (IC) reaction, occurring if Ag is fixed within the tissues, and Ig circulates in bloodstream. This will cause bi-directional counter-diffusion and IC is formed in the zone of equivalent concentrations. The biological or clinical manifestation would be focus of necrosis, vasculitis, coagulation and thrombosis with leukocyte infiltration.
Atopy - clinical term designating the various local manifestations of anaphylaxis in sensitized hyperreactors. Also, a genetically controlled predisposition to develop localized anaphylactic reactions to inhaled or ingested allergens.
Autoallergens - normal intact self-antigens, commonly provoking autotolerance, but able to trigger autoallergy.
Autoallergy - excess of autoimmunity, caused by improper function of autoimmunity control mechanisms and/or by interference into anti-idiotypic network.
Autoimmunity - complex of physiological mechanisms based on self-recognition and self-addressed immune response. Serves for the purposes of complementary autoregulation.
Bezredka's method - the method for decreasing of anaphylactic sensitization by means of subdivided intradermic boosts, and than - hypodermic injections of anaphylactogen in small doses.
Blast-transformation - sequence of mitoses plus functional activation of monoclonal (oligoclonal) character triggered by complex of an epitope and MHC-protein, correspondent to the clonal TcR or clonal Ig-receptor. In blast-transformation, G0 and G1 phases get exceedingly shortened, S-periods and mitoses follow one after another.
B-lymphocytes - all cells capable to express and rearrange immunoglobulin genes and possessing CD19-CD21 markers.
Bypass of autoreactive T helpers - The autoallergy may be induced, even if they are eliminated or anergic. In this case autoreactive effectors are stimulated without any participation of anti-self helpers, by another helpers or by another direct mechanisms.
Bypass of regulatory mechanisms - a pathway of autoallergy which may be initiated due to disinhibition of autoreactive T-helper activity or failure of their deletion. As a result, autoreactive helpers promote the activation of existing (normally, silent) autoreactive effector clones.
Capping phenomenon - Ig cluster formation on the surface of B-cell, triggered by specific antigen or cross-reacting agents.
CD - "clusters of differentiation" or "cluster designation" - abbreviation used (with numeric indexes) to unify the designation of surface markers for immune, hematopoetic and other somatic cells
Cellular immunity - historical name for DTH.
Central organs of immunogenesis - those, where immature lymphocytes develop and are exposed to primary clonal selection (bone marrow, thymus).
Chymase - a chymotrypsin-like enzyme from mast cells, which destroys proteoglycans, thus increasing the permeability of vascular wall and basal membranes. Ch. stimulates also bronchial mucus production.
Class I HLA antigens - those, coded by three closely linked loci designated HLA-A, HLA-B, HLA-C and also by non-classic loci titled E, F and G. They take part in recognition of the antigens produced within APC or endocellular (do not confuse with endogenous of with self antigens). They normally present on all nucleated cells are recognized by CD8-positive cytotoxic lymphocytes.
Class II HLA antigens - those coded for in a region known as HLA-D. Normal constituents of antigen-presenting cell, B-cell and activated T-cell's plasma membrane. Obligatory participants in recognition of the antigens, exocellular for APC. Recognized by CD4+ lymphocytes.
Class III HLA molecules - traditional name for some humoral effectors of immune system, encoded in 6th chromosome between the genes of HLA I and II., to which they are non-homologous.
Clonal anergy hypothesis - concept of autoallergy origin, stating that lymphoid cells expressing receptors for self-antigens continue to exist in adult life but cannot be triggered to form antibody.
Clonal deletion hypothesis - a concept stating that autoimmune diseases result from the emergence of "forbidden clones" of lymphocytes reactive against self-antigens, probably owing to somatic mutations.
Clonal selection theory - an explanation of clonal diversity of lymphocytes, according which each particular lymphocyte can recognize and respond for limited number of epitopes, probably - only one epitope. According to second key statement of this theory, the specificity of lymphoid clones is achieved before primary contact with antigen, owing to stochastic recombination of hypermutable genes in somatic mutation process.
Communicative Regulatory Integrative Apparatus (CRIA) - neuroendocrine and immune system taken in their interactive regulatory interplay, established by cytokines, lymphocyte hormone production and physiological autoimmunity.
Complement - thermolabile system of plasma, responsible for lytic action of antisera over target cells, including at least 13 protein factors and 7 inhibitors. These regulators normally circulate in non-active form. They are able to self-assemble in response to certain immunological and non-immune signals. In this process they act as serine proteases and/or mutually correspondent receptors. The result of their function is cell lysis aimed by antibodies and trigger of inflammation.
Conformation determinants (syn. - discontinuous) - the epitopes formed by the spatial combination of the different portions of polymeric molecule, discontinuous in its primary structure.
Contact dermatitis - (in some clinical texts - also contact eczema) - a kind of DTH, characteristic for intraepidermic penetration of an allergen (or hapten), antigen-presenting via Langerhans' cells and epidermal edema (vesiculation) in clinical picture.
CREST syndrome - limited form of systemic sclerosis, which manifests as: calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly and telangiectasia
Cytokines - soluble polypeptide and glycoprotein mediators of relatively small molecular mass, mediating the signal interactions among cells of the immune system and between immune system and somatic cells.
Cytotoxic reactions - 2nd category of ITH, mediated via non-reagin isotypes of immunoglobulins towards cell antigens, in which cell injury is produced through Ig-dependent complement, opsonized phagocytosis and Ig-dependent cytotoxicity mechanisms.
Delayed type hypersensitivity (DTH) - immunopathological reactions, occurring without any contribution of circulating antibodies, exclusively through specific clones of cellular effectors.
Desensitization (syn.: hyposensitization) - decrease in allergic readiness of sensitized organism achieved by means of medical interference (artificial d.) or as a result of immune response (natural d.).
Disregulatory reactions - non-destructive reactions caused by signal action of autoantibodies against cell receptors, enzymes and chromatin elements.
Endocellular antigens - those alien and self exogenous and endogenous antigens, which are assembled (or persist) within antigen-presenting cells, processed through proteasomes and Golgi complex and presented in complex with Class I HLA proteins, thus triggering preferentially, but not exclusively, delayed hypersensitivity mechanisms.
Eotaxin - peptide autocoid, produced by epithelial cells and macrophages for chemoattraction of eosinophils, one of chemokines, essential for late phase of anaphylaxis.
Epibody (Ab2a ) - anti-idiotype directed against idiotope irrelevant to paratope. Unlike homobody, E. does not serve as internal immunologic image.
Epirestriction - phenomenon of idiotype-antiidiotypic interactions between different subsets of T-helper cells.
Epitope (or immunodominant region) - The minimal structural unit of an antigen, recognizable for antibodies and lymphocyte antigenic receptors.
Exocellular antigens - those alien and self exogenous and endogenous antigens, which are engulfed by antigen-presenting cells from exterior, by means of endocytosis, processed through lysosomes and presented in complex with Class II HLA proteins. Elicit, preferentially, although not exclusively, immediate hypersensitivity mechanisms.
Exocytosis - excretion of bactericidal agents and other inflammation mediators out of phagocyte during phagocytosis.
Extrinsic allergic alveolitis - immune complex inflammation, involving lung interstitial spaces and caused by Arthus-like phenomenon triggered by exogenous allergens from alveoli (Fungi, Bacteria) and circulating antibodies (from blood vessels). Causes a family of occupational and sporadic bronchopulmonary allergic diseases.
Fab -portion - The portions with NH2-ends of heavy and light chains (Fragments antigen-binding) variable and having different primary structure in antibodies of various specificity. Variable regions form a concave of unique shape, filled up with appropriate antigenic epitope. This end of molecule is used for binding of an antigen and bears the immunologic specificity of an antibody.
Fc-portion - Hydroxylic COOH-end of Ig molecule (Fragment crystallizable or constant). It has the same structure in all antibodies of every particular class and subclass, but differs in Ig, belonging to different subclasses and classes (isotypic variance). Fc-portion fulfills different biological functions in various classes of Ig, making them tools for different purposes.
Frustrated phagocytosis - phagocytosis completed with exocytosis instead of object engulfment. Observed in case of large objects (parasites) and small phagocytes (platelets). Causes significant tissue damage.
Glomerulonephritis - vasculitis of kidney tufts, always involves immune complex mechanisms, as a rule, in combination with other autoallergic reactions.
Graft-versus-host reaction (GVHR).- Aggression of immunologically active graft, containing T cells, which are not rejected because of antigenic similarity to host or due to host's immune deficiency, against host tissues.
Granulomas - the sites of allergen persistence and focal productive inflammation in DTH. Every granuloma is a group of chronically activated macrophages and their descends (epithelioid cells) plus attracted lymphocytes and other WBC. Cellular content of granulomas is replenished mostly by recruiting, but also by non-neoplastic local cell proliferation This process is driven by cytokines.
Granulomatous reaction - a kind of DTH in systemic spread and persistence of an allergen within the cells of macrophage lineage. Characteristic for production of granulomas.
Hapten - low molecular weight substance, capable to generate unique three-dimensional complexes with biopolymeric carriers and provoke specific immune response, having no its own continuos antigenic determinants.
Hay "fever" - pollinosis manifested in seasonal allergic rhinitis. Commonly proceeds without real fever.
Heteroallergens - a kind of neoantigens - endogenous antigens not ordinary for intact normal cells, but induced by infection or created as a result of alteration, thus giving start to allergy.
Heteroimmune reactions cytotoxic reactions against changed self antigens or epitopes, created by complexing of self cells with alien haptens of antigens.
HIV-infection (human immunodeficiency virus infection) - an epidemic retroviral disease characterized by profound immunosuppression associated with opportunistic infections, the development of neoplasms, and frequent involvement of the CNS, which can clinically manifest as acquired immunodeficiency syndrome (AIDS). The manifestations are caused by perish of CD4+ lymphocytes and persistence of HIV in macrophages and dendritic cells, including microglia.
Homobody - Ab2b - anti-idiotypic antibody, which could interact with the antigen-specific B-cell or T-cell (or even with somatic cell receptor) and deliver a stimulatory or a suppressive signal (being an internal immunologic image of the antigen). Thus, this kind of anti-idiotypic antibodies has the potential to regulate immune responses and is believed to perform such a function in vivo.
Horror autotoxicus thesis - Concept, which claims that no antibodies can be formed against body's own components in healthy organism (P. Ehrlich).
Humoral immunity - historical name for ITH.
Hyperreactors - individuals, genetically predisposed to anaphylaxis.
Hypersensitivity - in many European texts called also "allergy" - immune-mediated tissue-damaging reaction. In clinical language - any adverse immune reaction, which is too intensive or qualitatively unusual, because it brings pathological sequels. The clinical usage of this term is not precise and somewhat misleading.
Idiotype - The set of idiotopes located on specific monoclone of antibodies.
Idiotīpe - The whole paratope, or its part, involved in immunologic interactions as an antigen.
Immediate type hypersensitivity (ITH) - immunopathological reactions in which circulating immunoglobulins are essential and obligatory for the mechanism.
Immune complex (IC) reactions- 3rd category of ITH, in which circulating antibodies of different classes bind soluble of affixed antigens and form complexes with abnormally decreased clearance. IC are not eliminated properly, but sediment on endothelium or other tissue structures, causing activation of cascade proteolytic mediators and clotting. This is resulted in vasculitis and/or other forms of inflammation. The fractions of complement then attract and activate neutrophils, which, partly through the release of neutrophilic lysosomal enzymes, produce tissue damage.
Immune system. - Special system capable to create and archive the addressed protective programs individually picked up in relation to concrete pathogens. This system is based on inducible protein biosynthesis, and, if necessary, displays the property to unzip these programs from archive and to carry them out in the amplified (strengthened) form. This system has sensory functions as regards to the molecular nature of self and aliens biological polymers; it possesses the memory of the previous signals and learning ability. By virtue of these features the repeated answers on the same pathogen differ from initial one.
Immunogeneicity - the property to induce immune response.
Internal immunologic image - (syn. Homobody, Ab2b ) - Anti-idiotypic antibody against paratope of an antibody, imitating more or less precisely immunological and sometimes - also biological signal properties of the antigen.
Isoimmune reactions (also alloimmune r.) - cytotoxic reactions against alien cells.
Isotypic switching - Swap of Ig-classes in course of immune response, controlled by T-helpers via cytokines and by complement fragments.
K-cells - collective designation for the cells of different lineage (macrophages, lymphocytes, eosinophils, NK-cells) possessing the Fc-receptors and able for antibody-dependent cellular cytotoxicity.
Langerhans' cells - antigen presenting cells within the epidermis.Their particular morphological sign is the tennis-racket-shaped Birbeck's granule.
Langhans' or Pirogov-Langhans' cells - descends of epithelioid cells in infectious granulomas, fused and transformed into giant multinucleated cells (typically, with peripheral location of nuclei).
Lipopolisaccharides (LPS) - thermostable components of bacterial capsule in gram-negative encapsulated germs. Contain polysaccharide O-antigen plus lipid A. Potent activators of immune system and chemoattractants. Also are known in infectious immunology as "endotoxins" and " exogenous pyrogens", for ability to provoke toxico-septic shock, acute phase response and fever.
Lymphadenitis - The enlargement of lymph nodes accompanied with the inflammation of the node itself and adjacent tissues. In cases like this the node contains some unusual cells immigrated from bloodstream and, quite often - also some infectious germs, persisting within the cells.
Lymphadenopathy enlargement of lymph nodes observed due to reactive hyperplasia of their lymphoid cells in course of the immune response. It is local (in inflammation) or systemic (in antigenemia, e.g. viremia). In these cases lymph node has normal cellular content, although the number and size of follicles is greater. The spectrum of autocoids in the node is represented with cytokines exclusively.
Memory cells - all T- and B-lymphocyte appeared after primary immune response as a result of clonal selection and antigen-induced clonal expansion process.
MHC-proteins (HLA-antigens) - highly polymorphic membrane glycoproteins, encoded by multigens and serving as markers of self cells. They take part in the formation of the antigen-containing complex, recognized by lymphocytes during immune response. In this role, histocompatibility proteins are able to influence the orientation and the very choice of epitopes, presented to lymphocytes. This is essential for distinguish between self and alien antigens and for determination of strength and character of immune response. Some alleles of MHC are in linkage disequilibrium with genes controlling the predisposition to certain disiases.
Mitogenic lymphocyte stimulation - Non-speciphic polyclonal activation of T- (and also B-) lymphocytes started by polyclonal activators or mitogens (e.g. plant lectins). These agents bind the surface mitogenic receptors of lymphocytes, located on many various clones, so the response involves simultaneously a lot of different lymphoid clones. As a rule, polyclonal responce is much weaker in comparision with regular monoclonal one, provoked by antigen-specific one. Mitogenic stimulation, in difference with antigenic blast-transformation, does not trigger the serial cell divisions, but is limited with one mitosis.
Natural killers or NK-cells (null-cells) - cellular elements with the morphology of large granular lymphocytes, which do express neither surface Ig, nor TcR, hence they do not possess CD3 marker. Due to this, NK-cells are not enlisted into B- or T-lymphocytes. The marker of these cells is surface Fc-receptor of IgG (antigen CD16). NK are capable to recognize and kill virus-carrying cells and tumor cells, as well as some targets of autoallergy, without preliminary sensitization and either regardless the HLA-restriction, or with restriction by self MHC Class 1 antigens only. Special receptor of NK-cell binds still unknown ligands of target cell.
Naturally occurring autoantibodies - physiological autoreactive Igs, directed against most common autoantigens (DNA, thyroglobulin, myelin, hormones and their receptors, Fc-fragments, heat shock proteins), which have epitope structure, close to highly spread exoantigens. Natural autoreactive Igs belong to M class and are produced on initial stages of primary immune response by special subset of CD5-positive B-cells (constituted for almost 20% of all B cells). Their variable chain domains are encoded for germ cell line genes Vn3-n5 and may be regarded as rudiments of some ancient less selective mechanisms of primary immune response.
Negative immunologic memory - the same as acquired immunologic tolerance, when first contact with an antigen changes the immune system in such a way, that repeated stimulation causes no response or produces decreases response.
Negative selection - elimination of the lymphoid clones, unable to react with self HLA-antigens (I and II classes) and also extinguishing of T-precursors, which are capable to respond on self unique sequential epitopes, complexed with self HLA-glycoproteins (I and II classes), i.e. potentially autoreactive ones.
Nephritic (nephritogenic) factor - The autoantibodies towards alternative complement pathway convertase - C3bBb-fragment, which cause in some patients C3b deficit and membranoproliferative glomerulonephritis of II type. They activate and stabilize convertase of alternative pathway, promoting progressive loss of C3 and decrease of IC clearance rates.
Network theory - the concept, which claims that immune response is mainly regulated by physiological anti-idiotypic autoimmunity.
Non-specific desensitization - achieved through the mechanisms of non-specific immunosuppression, e.g. by means of cytostatic drugs.
Opsonins - chemoattractants presented on the surface of engulfed cells and capable to bind phagocyte's receptors.
Opsonization - facilitation of phagocytosis via acceleration of its attachment and engulfment stages.
Paratope - Epitope-fixing area of an immunoglobulin, peculiar in every antibody of a given specificity, and , in turn, antigenic.
Passive immunization - provision of temporary protection by means of exogeneously produced immune effectors.
Peripheral lymphoid organs - those, where mature lymphocytes live, undergo antigen-dependant clonal expansion and carry out the immune responses. Do not contain epithelial cells, producing differentiating cytokines. (Among them: spleen, lymph nodes, Waldeier-Pirogov lymphoepithelial pharyngeal ring, appendix, Peyer's patches and diffuse non-encapsulated lymphoid elements of bronchial and urogenital mucosa). Some authors regard bone marrow as both central and peripheral lyphoid organ at the same time.
Phagocytosis - a kind of receptor-mediated endocytosis, applied for engulfment of relatively large objects (1 mcm and greater) with assistance of microfilaments.
Plasma cells - functionally active antibody-secreting descendry of B-lymphocytes, which are devoid of any surface immunoglobulins, but carry surface marker PC-1.
Pollinosis - local anaphylaxis caused by inhalation of plant pollen (masculine hametes of plants).
Positive immunologic memory - Figurative traditional name for the antigen-specific phenomenon of boosted secondary immune response after repeated penetration of the same antigen.
Positive selection - choosing of the lymphoid clones, capable to recognize the unique alien sequential epitopes in complex with self HLA-glycoproteins (I and II classes).
Prausnitz-Kustner reaction - induction of local skin sensitization to anaphylactogen by means of passive immunization in the form of donated serum injection to recipient.
Primary immune response - non-boosted answer of immune system after 1st contact with an antigen. It gives noticeable titers of circulating antibodies 1-2 weeks after start. Maximal antibody production is achieved 1-2 months later, than their concentration declines. IgM are initially predominant in primary response, with later rise in Ig G titers.
Primary immunodeficiencies - the states when the ontogenesis of immune system is altered, giving start to congenital or acquired deviations, manifested in failure of immune responses. These disorders were called immunodeficits or immune deficiencies.
Priming - Proliferation of lymphoid clones in central organs of immunogenesis, accompanied by development of their clonal diversity, as well as positive and negative selection to achieve autotolerance.
Prions - the simplest among all exogenous pathogens pre-cellular obligate parasites, devoid of nucleic acids.
Quilty effect - subendocardial lymphoid infiltration in heart transplant.
Reagins - (also called homocytotropic or cytophilic antibodies): immunoglobulins able to bind special kind of Fc-receptors on some cells and sensitize them for anaphylactic reactions ( in humans IgE and IgG4, in rodents - IgE and IgG4.).
Regional Lymphoid Systems Associated with the Mucosa - multiple non-encapsulated lymphoid elements, residing in lamina propria of the mucous membranes and in submucosal layer. B cells of this compartment produce IgA, T cells are specific for they belong to minor subset of T-lymphocytes with g s - type of antigenic receptors.
Reticulo-endothelial system (RES) - combined group joining all functionally related endothelial and phagocytic cells (both settled and nomadic) - related to antigen presentation and using cell adhesion molecules for their function .
Rheumatoid factors- antiisotypic autoantibodies towards Fc-portions of self immunoglobulins. Present in rheumatoid arthritis and some other autoimmune non-organospecific and IC diseases. Cross-react with core histone complex and some proteins of Cocci..
Sanarelli's phenomenon - induction of toxic shock in animals by repeated i/v injection of LPS, as a result of allergoid reaction (also known as generalized Schwartzman's phenomenon).
Schwartzman's phenomenon - local variant of Sanarelli's phenomenon, manifested as focus of coagulation, thrombosis and necrosis at the place of first i/d injection of LPS after repeated i/v injection of LPS, an allergoid reaction.
Secondary immune response - boosted answer of the immune system, triggered if the antigen is already known to organism. Repeated exposure produce more rapid and strong response, with registerable titer of specific antibodies achieved as early as in few days, with much higher maximal level, remaining stable for many months. Ig G predominates from the very beginning of secondary immune response.
Secondary immunodeficiencies - those arising as complications of infections (including HIV-infection), malnutrition, aging, or side effects of immunosuppression, irradiation, or chemotherapy for cancer and other autoimmune diseases.
Sensitization - term used in Allergology to designate a primary immune response for a given allergen.
Sequential determinants (syn. - continuous) - the epitopes formed by primary sequence of monomers in polymeric molecule, kept intact after antigen processing.
Serum sickness - the disease caused by parenteral injection of and systemic exposure to alien proteins, combines the mechanisms of systemic immune complex vasculitis and anaphylotoxin-mediated allergoid reaction (in acute phase) with delayed hypersensitivity (in late phase).
Severe combined immunodeficiency disease (SCID) - an extremely serious form of inherited primary immunodeficiency syndrome characterized by defects in both T cell-mediated and humoral immunity, most severe among the whole group of primary immunodeficits.
Slow - reactive substance of anaphylaxis (SRS-A) - the mixture of LtC4D4E4, involved not only in early, but also in late phase of anaphylaxis.
Specific desensitization - established via antigen-specific or idiotype-specific immunosuppression, e.g. by small doses of the appropriate allergen
Status thymico-lymphaticus - marginal variant of reactivity (diathesis) characterized by delay of thymic gland accidental involution, hyperplasia of thymus, hypoplasia and subnormal function of adrenal cortex and some other endocrine glands, predisposition to autoallergy and severe reactions towards commonly non-pathogenic stimuli (narcosis etc. ). S. th. was associated with sudden infant's death syndrome.
Superantigens - T-cell activation messengers capable to stimulate the T-cells carrying some variants of TcR in oligoclonal manner, regardless of their precise antigenic specificity, which is bypassed. The mandatory attribute of a superantigen is simultaneous correspondence between a portion of its molecule - and some unique variant of TcR, and between another portion of the same superantigen molecule - and HLA class II glycoprotein. S. are blamed for many severe allergoid reactions, like toxic dyspepsia and some kinds of toxic shock.
Suppression - Prevention and arrest (or decrease) of immune response. Occurs in central lymphoid organs an on periphery.
Suppression (peripheral) - group on mechanisms decreasing the activity of mature autoreactive lymphocytes. Includes antigen-specific, idiotype-specific and non-specific suppression via function of different lymphocytes - CD8+ cytotoxic ones; CD4+ Th2-suppressing lymphokine producents, and antiidiotypic autoimmunity against autoreactive effectors realised by B-cells.
Suppressor lymphocytes - Some clones of CD8+ T-cells, CD4+ T-cells, as well as certain B-cells serving to suppress the immune responses. These regulatory functions are mediated for the most part by the secretion of soluble cytokines, but also through incomplete killing effect and even via antiidiotypic autoantibodies. S. l. is not a distinct subset or cell lineage within lymphoid cells, but functional group, heterogeneous in origin.
Systemic anaphylaxis - (also called anaphylactic accident, anaphylactic shock) - multiorganic failure as a result of systemic action of inflammatory autocoids, released in course of immediate hypersensitivity after injection of an allergen into bloodstream of sensitized hyperreactor.
T-helpers - T-cells which regulate by means of different cytokines the function and growth of other T-cells, B cells, hematopoietic and, probably, also other somatic cells. Their immunoregulating functions are expressed either as facilitation or as suppression of the response. They are CD4+ and provide "help" in the generation of cytotoxic T cells (Th1) and antibody-secreting B cells (Th2). Via CD4 molecules, T-helpers bind to class II molecules of the major histocompatibility complex on antigen-presenting cells and recognize continuous epitopes of processed antigens.
T-independent antigens -antigens, which include panels of numerous identical epitopes. Among them bacterial lipopolysaccharides, polymeric protein of Flagellates-flagellin, dextran, levan and other bacterial capsule polysaccharides, ficoll and polypeptides composed of D-amino-acids. They are hardly digestible for antigen-presenting cells, but able to cross-link the recognizing lymphocyte receptors directly. This group of antigens provokes polyclonal B-cell activation and immunoglobulin production without obligatory T-cell cooperation
T-killers - traditional name for cytotoxic CD8+ subset of T-cells, capable for recognition of the unique antigens complexed with class I MHC glycoproteins on any cell and direct liquidation of target cells, by means of perforin-mediated lysis.
T-lymphocytes - lymphoid cells expressing and rearranging TcR-genes (CD3-positive). Unlike B cells, none of T-cells is not able to be triggered by any of free antigens, requiring antigen-presenting cells cooperation.
Toxoid - bacterial toxin, modified for the purposes of active immunization as to loss the toxic activity, but still immunogenic.
Tryptase - the marker enzyme of mast cells; causes lysis of C3 complement fragment with production of its decay peptide anaphylotoxin C3a . T. also is competent to activate kinin system and, via it, the whole cascades proteolytic multi-system of blood plasma. Basophils produce the analogue of tryptase, activating kinins.
Tuberculin-like reaction - a kind of DTH in deeper penetration and persisting of an allergen (hapten) within the dermis; as a rule allergen is presented by skin dendritic cells and reaction is manifested in papulous dermatitis.
Vasculitis - the common manifestation of any systemic disorder of immune complexes' clearance, an important manifestation of rheumatic and many other diseases.
Veto-effect - Negative selection phenomenon, realized by CD8+ cytotoxic cells, which express self-antigens in the context of HLA 1st class glycoproteins and eliminate the autoreactive immature T-cells.