From Big Medical Encyclopedia

IMMUNOCOMPETENT CELLS (Latin immunis the free, saved from something + competens suitable for competent [is] corresponding) — the cells capable to specifically distinguish antigen and to answer it with an immune response. Such cells are T - and B-lymphocytes (timuszavisimy and marrowy lymphocytes) which under the influence of alien antigens (see) are differentiated in a sensibilized lymphocyte and a plasmocyte.

Intensive studying of genesis and physiology of immunocompetent cells belongs to the 70th 20 century. The term «immunocompetent cell» was offered by F. Burnett in 1961 as the basic concept of the klonalnoselektsionny theory immunity (see). Symbols of T - and B-lymphocytes are entered by Roytt (I. M of Roitt) in 1969.

Fig. 1. The diffraction pattern of the B-lymphocytes capable to specifically «distinguish» antigen at the level of humoral immunity. Microvillis are expressed (are specified by shooters).
Fig. 2. The diffraction pattern of the T lymphocytes capable to specifically «distinguish» antigen at the level of cellular immunity. Microvillis are not expressed

Morphologically T-and B-cells are lymphocytes, indiscernible in a light microscope, however in the scanning supermicroscope on B-lymphocytes the microvillis which are absent on T lymphocytes (fig. 1 and 2) come to light. T - and B-lymphocytes differ with specific antigens. And. to. have antigenraspoznayushchy receptors which density on V-cells is 100 — 200 times higher, than on T-cells.

On a surface of V-lymphocytes receptors are immunoglobin molecules; the nature of receptors on T lymphocytes remains insufficiently studied. On B-lymphocytes there are receptors for a Fc-fragment of immunoglobulins and the third component of a complement (SZ). Small part of lymphocytes has no superficial receptors; these cells are called O-cells. Perhaps, it is early stages of a differentiation of T - and V-cells from predecessors or differentiated, but physiologically defective T - and V-cells.

T - and B-cells have ability to form sockets (education in which center there is a lymphocyte, and around not less than 3 — 5 erythrocytes) that can serve as the test for their differentiation.

The essence of rosetting consists in accession to a surface of a lymphocyte of heterological erythrocytes. To 85% of T lymphocytes of the person educate spontaneous sockets with erythrocytes of a ram whereas the quantity FATE with erythrocytes among B-cells does not exceed 2%. In turn B-cells form sockets with erythrocytes of a ram to which surface complexes antigen — an antibody or antigen — an antibody — a complement were attached.

Among T-cells there are 2 subpopulations of lymphocytes: T1 — short-lived, found preferential in a thymus gland and a spleen, a little getting to a blood channel, highly sensitive to corticosteroids and slabochuvstvitelny to anti-lymphocytic serum, and T2 - long-living, intensively circulating in an organism, resistant to corticosteroids and sensitive to to anti-lymphocytic serum (see). Possibly, cells of T2 are later stage of a differentiation, than T1 cell.

Predecessor I. to. the multipotentny stem hemopoietic cell, self-sustaining in marrow of mature animals is. In a bone brain there is the first stage of its differentiation in a semi-stem cell, the predecessor I. to. The subpopulations of this cell which are differentiated in In - or T lymphocytes, however specific T - and B-antigens and superficial receptors at these cells are revealed, apparently, not yet. Semi-stem cells, getting to a thymus gland, under the influence of the specific inductor (Timosinum) turn into T lymphocytes which migrate in peripheral lymphoid bodies. B-lymphocytes are differentiated in Fabrition's bag at birds and in lymphoid body of mammals. It is supposed that it are peyerova of a plaque. Population of B-cells is supported in marrow. T - and B-cells are located in various sites of peripheral lymphoid bodies (see. Adenoid tissue ) and constantly circulate on circulatory and limf, to vessels. Under the influence of alien antigen T lymphocytes are differentiated in sensibilized lymphocytes, and V-lymphocytes — in plasmocytes (see) which carry out specific immune responses of cellular and humoral type.

Process of a differentiation of B-cells in antiteloprodutsiruyushchy under the influence of the majority of antigens requires interaction of T - and B-cells with the participation of macrophages, and also the stromal cells creating a necessary microenvironment. At this interaction T-to a letka transfer to V-cells the nonspecific factor activating proliferation, and antigen becomes more active for induction in cells of synthesis of antibodies. The T-cells participating in interaction with B-cells and strengthening antibodyformation are called cells assistants (helper), and the T-cells causing braking of antibodyformation and participating in formation immunol. tolerances (see. unresponsiveness ) — cells suppressors. Suppressor function amplifies under the influence of antigen, but in itself is not specific. After influence of antigen and process of cooperation And. to. are differentiated in plasmatic and effector lymphocytes. Regulation of this process is also carried out by interaction of the differentiated populations of T - and V-cells. Part T - and V-cells after contact with antigen and initial activation does not pass a final differentiation, and is long remains in an organism. Such T - and V-lymphocytes are called cells of immunological memory. They provide at repeated hit in an organism of antigen more prompt, intensive secondary immune response.

Among specifically sensibilized T lymphocytes on their functions distinguish the cells killers having cytotoxic properties, which are carrying out the destruction of genetically alien cells, T-cells activating a large number of not sensibilized T lymphocytes, and also T-cells — the activators of macrophages strengthening phagocytosis.

The question of is intensively studied whether functional groups are And. to. the isolated gi-hundred-genetic subpopulations of T - and B-cells or each T - and a B-cell can perform at least a part of these functions at different stages of the activation and a differentiation.

Interaction of T - and V-cells, action on alien cells are carried out at the expense of products of the active agents called by humoral effectors, or lymphokines.

Methods of identification of T - and V-cells give the chance to determine the level of disturbance immunol, reactions at this or that stage of a differentiation of T - and V-cells, disturbance fiziol, characteristics at a number of the inborn and acquired immunodeficient diseases (see. Immunological insufficiency ).

Bibliography: Bernet F. M. Cellular immunology, the lane with English, M., 1971, bibliogr.; Petrov R. V. Immunology and immunogenetics, M., 1976, bibliogr.; Chertkov I. L. and F r and d e of N matte of A. Ya. Cellular bases of a hemopoiesis, M., 1977.

D. R. Kaulen, K. A. Lebedev.