From Big Medical Encyclopedia

LYMPHOCYTES (Latin lympha pure water, moisture + grech, kytos a receptacle, here — a cell; synonym: lymphoid cells, lymphoid elements) — kind of agranulocytes.

The term «lymphocytes» appeared in the middle of 19 century for designation of cells, to-rye are a part of a lymph of mammals. Idea of a role of L. there were in the 70th 20 century on the basis of experimental data at a blood analysis, a lymph and bodies of a hemopoiesis. L. — the simplest on the cell structure of an animal organism. However they possess a wide range funkts, opportunities, especially at the highest vertebrata, napr, stem cells of all fabrics — derivatives of a mesenchyma — have L. V appearance a body of the person L. are distributed in such a way that about 1300 of L. is in limits of connecting fabric, apprx. 100 g — in marrow, apprx. 100 g — in an adenoid tissue and apprx. 3 g — in blood. L. treat the most mobile cells of an organism; they extend with a blood flow and a lymph.

At the person L. begin to be formed at the end of the 2nd — the beginning of the 3rd week of development of an embryo in a mesenchyma of a wall of a vitellicle of a germ along with development of vessels. During embryonal blood formation of L. are formed also in a liver, a spleen, limf, nodes, in a thymus and marrow. In the postembryonal period normal they form only in marrow, a spleen, limf, nodes and in limfoepitelialny educations.

Fig. 6. Diffraction pattern of ultrathin section of a small lymphocyte: 1 — a kernel with conglomerates of chromatin; 2 — mitochondrions; X 15 000.

L. have an appearance roundish (at rest) or extended (in a condition of active movement) the cells consisting of a kernel and rather small rim of cytoplasm. Size L. from 5 to 13 microns, and a cellular kernel — 3 — 12 microns fluctuate. Form and sizes L. depend on whether there are they in suspension or are attached to any substrate. Morphologically distinguish small L. to dia. 5 — 9 microns, average and big, to dia. 10 — 13 microns. Depending on a nucleocytoplasmic ratio distinguish uzkoplazmenny and shirokoplazmenny L. According to a phase of a life cycle allocate mature forms of H.p. with a small kernel and a diploid set of chromosomes, unripe (transitional L. or about lymphocytes) with middle ring and intermediate, between di - and tetraploid, a set of chromosomes and lymphoblasts — H.p. a big kernel, di - and a tetraploid set of chromosomes. On degree funkts, activities distinguish the based and activated forms L. On cytophysiological signs allocate short-lived L. (at the person L., the living 3 — 7 days, make about 20% of total quantity of L.), long-living (up to 100 — 200 days and more), recirculating — temporarily and repeatedly circulating between blood, a lymph and connecting fabric, and also slaborezistentny and resistant L. (e.g., in relation to the osmotic pressure, pH, effect of hormones, ionizing radiation, etc.). In blood of adults it is normal of L. make 19 — 37% of total quantity leukocytes (see). Most of them belongs to small mature uzkoplazmenny long-living L. Yadro of small L. occupies almost all volume of a cell. Cytoplasm surrounds it in the form of very narrow rim, often badly distinguishable in a light microscope. Atypical L have the reniform, jagged or segmented form of a kernel. (so-called forms of the Reader). In a supermicroscope on the periphery of a kernel along the double nuclear membrane penetrated by not numerous time electronic and dense glybk of heterochromatin (basichromatin) are visible, between to-rymi distinguish small sites rykhlo the located less dense euchromatin (fig. 6). In a kernel there are one or several kernels. All kernel is filled with electronic and transparent nucleohyaloplasm. In cytoplasm among an electronic and transparent hyaloplasma usually there are following organellas: a microcentrum (around emboly of a nuclear envelope), several mitochondrions, poorly developed lamellar complex, not numerous tubules of a cytoplasmic reticulum and the attached or free ribosomes and polyribosomes. Besides, in cytoplasm of small L. not numerous inclusions meet: the single lysosomes corresponding azurophilic to the granules seen in a light microscope, multibubbly little bodies, phagosomas, granules of a glycogen, a liposome, a few pinotsitozny bubbles. Often small L. has a set of usually finger-shaped shoots on the surface, to-rye clearly are visible in a raster supermicroscope.

Average mature L. have wider cytoplasm. At the activated L. it can be extensive and contain a large number of organellas. Unlike mature, unripe (big) L. have a big kernel, in Krom the share of the friable euchromatin which sometimes is evenly filling all kernel is increased; there are one or several large, well developed kernels, the number of nuclear pores is increased that demonstrates preparation of a cell for division.

Ultramicroscopic structure of L. reflects intensity and specificity of the function which is carried out by them. Manifestation of specific function depends on qualitative and quantitative structure of the molecular receptors located on a cytoplasmic membrane of L. Receptors are built in a membrane in the course of its education and updating that is under genetic control.

L. begin to show the specific function in body tissues only at hit in the corresponding microenvironment. In this case they are affected by specific and nonspecific hormones and mediators — the molecules contacting certain receptors on a surface of L., as leads to transition of L. from a condition of rest in an active funkts, a state.

L. perform three main functions — hemopoietic, trofotsitarny and immunological, from to-rykh the first two have no sufficient actual evidence. Nek-ry researchers on the basis of experimental data believe that among L. there are stem (polipotentny) cells, to-rye are capable to self-maintenance and a differentiation in many directions, passing at the same time stages of progenitors of the erythroidal, granulotsitarny, lymphoid, monocytic and megakariotsitarny direction (see. Hemopoiesis ). So, in a thymus gland under the influence of hormone of Timosinum of L. are differentiated in T-to a letka; in an adenoid tissue under the influence of the local conditions including cellular and humoral influences, L. are differentiated in immunocompetent cells (see), responsible for manifestation humoral and cellular immunity (see); assume also that in connecting fabric under the influence of a microenvironment lymphocytes predecessors turn in macrophages (see), fibrocytes (see. Connecting fabric ), mast cells (see). It is not excluded that L. perform trofotsitarny function, edges is that these cells get into various fabrics and bodies and collapse there, thereby quickly delivering nutritious and plastic substances (nucleinic to - you, proteins, polysaccharides, etc.) to other cells. Immunol, function is performed by the B-cells responsible for development of the humoral answer in an organism that is expressed in synthesis of specific antibodies (immunoglobulins) and the T-cells responsible for development of both cellular, and humoral immunity by means of various humoral factors (lymphotoxins, a factor of activation of B-cells, a factor of a chemotaxis of the macrophages, etc.) defining the direction and force of an immune response.

Quality and quantitative standard of L., belonging to various funkts, classes, has crucial diagnostic importance at a number of diseases, napr, at hemoblastoses, immunodeficient, autoimmune and many inf. diseases. Are for this purpose developed special morfol., cytochemical, biochemical, biophysical, and immunol, methods of a research of lymphocytes.

See also Leukocytes .

Bibliography: Galaktionov V. G. Cellular receptors of immune system, Usp. sovr, biol., t. 80, No. 4, page 84, 1975, bibliogr.; Gurvich A. E., etc. Immunogenesis and cellular differentiation, M., 1978; L ing of H. P. Stimulation of lymphocytes, the lane with English, M., 1971; The Normal hemopoiesis and its regulation, under the editorship of N. A. Fedorov, M., 1976; X r at-shch about in N. G. Gistogenez of connecting fabric, M., 1976; Cytologic aspects of diseases of system of blood, under the editorship of E. I. Terentyeva and G. I. Kozints, M., 1978; Park B. H. a. G about about d R. A. Principles of modern immunobiology, basic and clinical, Philadelphia, 1974.

G. I. Kozinets, P. D. Bonartsev.