From Big Medical Encyclopedia

OPSONINS — the factors of blood serum causing sticking of microorganisms, the died cells or their fragments, indifferent particles to a surface of phagocytes and the raising speed and efficiency of phagocytal reaction. Strengthening of phagocytal reaction in the presence of blood sera of animals was observed I. I. Mechnikov (1895), Zh. Borde (1895), Denis, Leklef (J. Denis, J. Leclef, 1895), I. G. Savchenko (1901).

The term «opsonins» was offered for the first time in 1903 A. Wright and Douglas (S. R. Douglas), to-rye considered that O. act on a bacterium, preparing them for absorption by leukocytes. It turned out that O. of immune serums on activity and specificity of action, resistance to temperature and a nek-eye to other signs differ from O. of normal blood sera. For their designation F. Neyfeljd and W. Rimpau in 1904 entered the term «bakteriotro-pins», to-ry is a little used.

Lakes consist of thermolabile and thermostable factors of blood serum. The most important thermo labile O. is the fragment of the 3rd fraction complement (see), the designated C3b. It is formed in blood serum or fabrics at activation of system of a complement. At a classical way of activation the IgG complexes + antigen or IgM + antigen connect a fragment of a complement of C1, to-ry in the presence of calcium ions and magnesium activates components of a complement of C4 and C2. The activated G42 complex (SZ-convertase) splits a component of a complement

of SZ on two fragments: SZA and C3b; the last also has oisonichesky activity. Formation of a fragment of C3b comes from SZ also under the influence of the SZ-convertase resulting from activation by alien polysaccharides, lipopolisakha-rida and units of immunoglobulins of properdinovy system in the presence of ions of magnesium (an alternative way of activation). The educated fragment of a complement of C3b is adsorbed on a surface of particles and causes phenomena of opsonization and immune sticking (see). In blood serum usually there is a C3b-inactivator and, perhaps, other not identified proteins, to-rye split a fragment of a complement of C3b on two fragments not having oisonichesky activity: C3c which is in a liquid phase, and S3s1, adsorbed on particles. Nek-ry researchers revealed opsonic activity at activated by S5-and C4 fractions of a complement. The indirect impact on opsonic activity of blood sera is exerted by proteins of properdinovy system (see. Properdin ) and early fractions of a complement as their presence at system and turning into the activated form are an obligatory step of formation of a fragment of a complement of C3b. Presence at blood serum of thermolabile substances, in particular 5 — 6 s - the beta pseudoglobulins which are not relating to system of a complement, but having oisonichesky activity is supposed.

Action of the thermolabile O. which are present at fresh blood serum of people and animals is a little specific. They lose the activity under the influence of warming up at t ° 56 ° within 30 min., and also at storage, processing by poison of a cobra, an incubation with cell-bound immune complexes, nek-ry bacteria and particles.

Thermostable opsonic activity of blood serum is provided to hl. obr. antibodies (see), belonging to immunoglobulins of the class IgG, the subclasses IgGl and IgG3 (see. Immunoglobulins ). In this regard they are highly specific in the action. The issue of direct opsonic action of IgM-antibodies is not resolved; their indirect opsonic impact is undoubted since they have highly expressed ability to induce formation of a fragment of a complement of C3b. Immunoglobulins A have probably no direct opsonic activity, but units of this class of immunoglobulins, inducing formation of a fragment of a complement of C3b on an alternative way, increase opsonic activity of blood sera. Opsonic antibodies in small amounts can be present also at normal serums. There are facts indicating otssonichesky activity of serumal lysozyme (see) and C-reactive protein (see).

On rates and efficiency of phagocytal reaction (see. Phagocytosis ) a certain stimulating impact is exerted by many other factors (hormones, mediators of century of N of page, a lipoida, pH of the environment, temperature, etc.).

In group, separate of O., allocate chemotactic factors, to-rye promote accumulation of phagocytal cells in the place of defeat and exert the expressed stimulating impact on efficiency of phagocytal reaction (see. Mediators of cellular immunity ).

The mechanism of opsonic action is found generally out. In a phenomenon of opsonization at least two phases can be allocated with a fragment of a complement of C3b and IgG-antibodies: a phase of opsonization of particles and a phase of an attachment (attraction) of opsoniziro-bathing particles to a surface of phagocytal cells.

Mechanism of opsonization fragment of a complement of C3b. In the first phase on a surface of microbes or other organic and inorganic particles settle the C3b-molecules formed as a result of activation of a component of a complement of SZ on an alternative or main way. At once after connection with a fragment of a complement of C3b the particle is distinguished as alien and attached to a surface of phagocytal cells (the second phase) with the subsequent capture. Accession C3b-opsonizirovannykh of particles to phagocytes happens in the presence of bivalent cations on special receptors (C3b-retsegggorakh) of a surface of a cytoplasmic membrane of mononuclear phagocytes and neutrophils. These receptors collapse proteolytic enzymes and are steady against action of anti-macrophagic antibodies.

Mechanism of opsonization to IgG-antibodies and. In the first phase of opsonization antide-terminantny groups of antibodies unite to determinant groups of surface antigens of particles. This connection equally well proceeds at t ° 37 ° and 4 °. Interactions in a molecule of immunoglobulin result conformational changes, to-rye, according to nek-ry researchers, exert impact on efficiency of the second phase of opsonization. The phase of opsonization of particles antibodies, as well as others immunol, reactions, is highly specific. Especially it is important at infection of the person and animals with capsular and highly virulent microbes, opsonization to-rykh a C3b-fragment is ineffective.

In the second phase opsonizirovan-ny IgG-antibodies of a particle are attached by a Fc-fragment to Fc-pe-tseptoram of a cytoplasmic membrane of mononuclear phagocytes and neutrophils. Fc-receptors of a rezistentna to proteolytic enzymes, interact equally actively both at presence, and for lack of bivalent cations at t ° 37 ° and 4 °. Speed and durability of an attachment of particles depends on concentration of antibodies and their avid-nost (see. Aviditet ). The incubation of phagocytal cells with antiserums to them and Fc-fragments of IgG blocks Fc-receptors of phagocytes. On Fc-receptors of phagocytal cells not only particles, but also their microagglutinates are adsorbed.

Opsonic activity of antibodies amplifies in the presence of a complement. In this case on a surface IgG-opsonizirovannykh of particles happens activation of system of a complement on a classical way to education and adsorption of a set of C3b-molecules. The attachment of such opsonizirovanny particle to phagocytal cells occurs as immune sticking to C3b-receptors or on the mixed type — at the same time to C3b-and Fc-receptors that sharply increases the force of adhesion of particles with phagocytes and, therefore, leads to more bystry and effective capture.

Stimulation of phagocytal activity of macrophages. Pointed to this way of opsonization also. I. Mechnikov. The effect of opsonization at this way consists in an attachment of particles to a surface of phagocytes. However mechanism of this phenomenon other. Bonden, Sorkin (S. V. Boyden, E. Sorkin, 1960) revealed cytophilic antibodies on a surface of macrophages of immune individuals, to-rye on a number of signs are close to free olsoniche-sky antibodies. The macrophages bearing cytophilic antibodies (they are not on a surface of neutrophils), are capable to attach specifically particles to the surface but type of formation of a cell-bound immune complex and thus to strengthen phagocytal reaction. The cell-bound immune complex formed on a surface of a phagocyte, besides, can activate a complement software the main, but not an alternative way that even more strengthens an attachment.

Are available this, testimonial of active participation of O. in processes of capture and digestion of particles. Griffin (F. The m of Griffin) et al. (1975, 1976) showed that the contact of opsonizirovanny IgG-or C3b-molecules of a particle with receptors of a membrane of phagocytes serves as a signal for emergence of changes in structure of actin and the microvillis leading to lengthening of pseudopodiums, conformal coating of particles by them and to formation of invaginations and vacuoles. And the conclusion of a particle in vacuoles (phagosomas) results from coupling of the molecules O. located on all surface of a particle with the receptors which are on a surface of pseudopodiums and invaginations. Also O.'s participation in digestion of bacteria is established. The mechanism of the phenomenon, close to phagocytosis — pinocytic (see) probably also includes a phase of opsonization.

Thus, modern knowledge of O. and opsonization indicates their extremely important role in protection of an organism of people and animals against an infection and in maintenance of constancy of internal environment of an organism (see. Immunity ). One of proofs of it is hypersensitivity of an organism to activators inf. diseases in cases of the hereditary or acquired defect of cells or deficit of the substances participating in products and activation of SZ and IgG (see. Immunological insufficiency ).

For assessment of opsonic activity of whole blood and its serum definition of an opsonic index, opsonofagotsitarny index and caption of the Lake is used. Increase in indicators of these tests at patients in comparison with healthy people or during a disease is estimated as a favorable predictive sign, weak increase or lack of that — as an adverse sign.

Understand the relation of phagocytal number (number of fagotsitirovanny particles, private from division, into number of phagocytes) of the studied blood serum to phagocytal number of normal serum as an opsonic index. As object of phagocytosis during the definition of an opsonic index standard strains of gram-negative bacteria are used. The opsonic index reveals the changes of opsonic activity caused by changes in system of a complement.

The Opsonofagotsitarny index, unlike o'lsonichesky, reflects changes of both opsonic properties of blood serum, and phagocytal activity of leukocytes of the patient to the specific activator. The method of calculation of an opsonofagotsitarny index at different diseases is various.

O.'s caption quantitatively characterizes force of opsonic activity of blood serum in relation to a specific disease-producing factor. Unlike opsonofagotsitar-ache reactions influence of changes is excluded here from phagocytes as in experience leukocytes or macrophages of the healthy person or an animal undertake.

In a wedge, practice definition of opsonic activity of whole blood or its serum is used at a brucellosis, whooping cough, diphtheria, rickettsioses and other diseases. Judgments of the value of this test are contradictory that is generally connected with labor input and imperfection of techniques.

Bibliography: Ado A. D. Pathophysiology of phagocytes, page 100, M., 1961; Andreyev V. P. and Podoprigora G. I. Modern methods of studying of the opsonizing activity of blood serum, Laborat. business, No. 8, page 479, 1977; Swordsmen I. I. Nevospriimchivost in infectious diseases, M., 1947; The Multivolume guide to microbiology, clinic and epidemiology of infectious diseases, under the editorship of H. N. Zhukova-Verezhnikov, t. 3, page 157, M., 1964; Griffin F. M of Opsonization, in book: Biol, amplification syst. immunol., ed. by N. K. Day a. R. A. Good, p. 85, N. Y., 1977; R o i t t I. M. Essential immunology, Oxford, 1979; Stossel T. P. Phagocytosis, New Engl. J. Med., v. 290, p. 717, 774, 833, 1974; Wright A. E. a. Douglas S. R. An experimental investigation of the role of body fluids in connection with phagocytosis, Proc. roy. Soc. B., v. 72, p. 357, 1903 —1904.

A. P. Krasilnikov.