Immunity

Evolution formed system of immunity about 500 million years. This masterpiece of the nature admires us with beauty of harmony and expediency. Persevering curiosity of scientific different specialities has opened before us patterns of its functioning and has framed last 110 years a science "Medical immunology".

Every year brings opening in this roughly developing area of medicine.

The logic prompts, that the immunity system protects us from infectious agents: bacteria, viruses and the elementary, i.e. Protects an organism from all foreign. But, at the same time became clear, that the immune system is necessary, first of all, for protection from, become to the stranger. The matter is that daily in our organism there are millions mutant cells which can become a source of lethal tumours.

Distinguish specific protection, or immunity, and nonspecific resistibility of an organism. Last unlike immunity is referred on destruction of any foreign agent. The system of a complement natural cytotoxycity, action of interferons, a lysozyme concern nonspecific resistibility, b-lysines and other humoral factors of protection a phagocytosis and pinocytosys.

Immunity is a complex of the reactions referred on maintenance of a homeostasis at an occurring of an organism with agents which are regarded as foreign irrespective of, whether they are formed in the organism or arrive in it from the outside.

Foreign bonds for the given organism, capable to cause the immune answer, have received the name "antigens". Theoretically any molecule can be an antigen. As a result of antigen action in an organism antibodies are formed, lymphocytes thanks to what they get ability to take part in the immune answer are sensitised. Specificity of an antigen consists that it selectively reacts with certain antibodies or the lymphocytes appearing after hit of an antigen in an organism.

Ability of an antigen to cause the specific immune answer is caused by presence on its molecule numerous a determinant (epytons), to which specifically as a key to the latch, the active centres (antideterminants) of formed antibodies approach. Antigens, co-operating with the antibodies, form immune complexes. As a rule, antigens are molecules with high molecular mass; there are potentially active substances in the immunologic relation which size of a molecule corresponds to one separate antigenic a determinant. Such molecules wear the name of haptens. The last are capable to cause the immune answer, only being bridged with a full antigen, i.e. Fiber.

The organs which are taking part in immunity, divide into 4 groups:

• Central - a thymus, or thymic gland, and, apparently, an osteal brain.
• Peripheric, or secondary, - lymph nodes, a lien, system of the limfo-epithelial formations located in mucosas of various organs.
• Behind a barrier CNS, spermaries, eyes, a parenchyma of a thymus and at pregnancy - a foetus.
• Intrabarrier - a skin.

Distinguish cellular and humoral immunity. Cellular immunity is referred on destruction of foreign cells and tissues and caused by action T-killers. A typical example of cellular immunity is reaction of tearing away of foreign organs and tissues, in particular a skin replaced from the person to the person.

Humoral immunity is provided with formation of antibodies and caused basically by function of B-lymphocytes.

Immune answer

In the immune answer, regulatory (regulating a current of immune reactions) and effectors of the immune answer (carrying out the final stage immunocompetent cells which can be parted on antigenrepresenting (representing antigens take part in struggle against antigens).

To antigenrepresenting to cells monocytes and macrophages, endothelial cells, skin pigment cells (Langerhans cell) concern, etc. regulatory cells concern T - and B-helpers, suppressors, countersuppressors, T-limfotsity memories. At last, to effectors of the immune answer belong T - and B-killers and the B-lymphocytes which are in basic antibody producers.

The important role in the immune answer is taken away to the special cytokines which have received the name of interleukines. From the name it is visible, that IL provide interrelation of separate kinds of leucocytes in the immune answer. They represent small albuminous molecules with molecular mass 15000-30000.

• IL-1 - The bond allocated at antigenic stimulation with monocytes, macrophages and others antigenrepresenting cells. Its action basically is referred on T-helpers (amplifiers) and MACROPHAGES-effectors. IL-1 suscitates hepatocytes thanks to what concentration of the fibers which have received the name rectantes of an acute phase as their maintenance is always enlarged in an acute phase of an inflammation increases in blood. The fibrinogen, S-jet fiber concern such fibers, an a 1-antitrypsin, etc. Fibers of an acute phase of an inflammation play the important role in a reparation of tissues, bind proteolytic enzymes, regulate cellular and humoral immunity. The concentration augmentation rectentes an acute phase is the adaptive reaction referred on liquidation of pathological process. Besides, IL-1 strengthens a phagocytosis, and also accelerates growth of blood vessels in damage zones.
• IL-2 It is allocated T-amplyfier under the influence of IL-1 and an antigen; is a growth factor for all kinds T-lymphocytes and the activator of K-cages.
• IL-3 It is allocated suscitated T-helpers, monocytes and macrophages. Its action is referred mainly on growth and development of mast cells and basophils, and also precursors T - and В-lymphocytes.
• IL-4 It is produced basically suscitated T-helpers and possesses extremely wide spectrum of action as promotes growth and differentiation B-lymphocytes, activates macrophages, Т-lymphocytes and mast cells, induces production immunoglobines separate classes.
• IL-5 It is allocated suscitated T-helpers and is the factor of a proliferation and a differentiation of eosinocytes, and also В-lymphocytes.
• IL-6 It is produced suscitated by monocytes, macrophages, an endothelium, T-helpers and fibroblasts; together with IL-4 provides growth and differentiation В-lymphocytes, promoting their transition in antibody producers, i.e. Plasmocytes.
• IL-7 It is originally allocated from stromal cells of an osteal brain; strengthens growth and a proliferation T - and В-lymphocytes, and also influences development of thymocytes in a thymus.
• IL-8 It is formed suscitated by monocytes and macrophages. Its appointment is reduced to intensifying of a chemotaxis and phagocytic activity of neutrophils.
• IL-9 It is produced Т-lymphocytes and mast cells. Its action is referred on intensifying of growth Т-lymphocytes. Besides, it promotes development of erythroidal colonies in an osteal brain.
• IL-10 It is formed by macrophages and strengthens a proliferation of mature and unripe thymocytes, and also promotes a differentiation of T-killers.
• IL-11 It is produced by stromal cells of an osteal brain. Plays the important role in a hemopoiesis, especially a thrombocytopoiesis.
• IL-12 Strengthens cytotoxicity of T-killers and К-lymphocytes.

The immune answer begins with interaction antigenpresented cells with an antigen then there is its phagocytosis and processing to products of degradation which are allocated outside and appear outside of antigenpresented cells.

Specificity of the immune answer is provided with presence of the special antigens which have received at mice the name of Ia-fiber. At the person its role is carried out by human leukocytic antigens of 2nd class, type DR (Human Leukocytes Antigens, HLA).

Ia-fiber is practically on all hemopoietic cells, but is absent on mature Т-lymphocytes; under the influence of interleukines there is a fiber expression on these cells.

The Ia-fiber role in the immune answer is reduced to the following. Antigens can be distinguished immunocompetent cells only at contact to specific receptors, however the quantity of antigens is too great also the nature has not prepared for them corresponding number of receptors, that is why the antigen (another's) can be learnt only in a complex with "" which function carries Ia - fiber or antigens HLA-DR.

Products of degradation of antigens, having left a macrophage, partially enter interaction with Ia-fiber, forming with it a complex suscitating activity antigenpresented of a cell. Thus the macrophage starts to cosecrete a number of interleukines. IL-1 operates on T-amplifyer therefore the last has a receptor to complex Ia-белок+АГ. This reaction, as well as all the subsequent, provides specificity of the immune answer.

Activated T-amplifyer allocates IL-2, operating on various clones T-helpers and the cytotoxic lymphocytes which are taking part in cellular immunity. Initiated clones T-helpers cosecrete IL-3, IL-4, IL-5 and IL-6, making primary impact on effectors a link of the immune answer and by that promoting transition B-lymphocytes in antibody producers. Thanks to it antibodies, or Immunoglobines are formed. Other interleukines (IL-7, IL-9, IL-10, IL-12) influence an outgrowth and a differentiation T - and B-lymphocytes and are the factors of reliability providing the immune answer.

Cellular immunity depends on action of the humoral factors allocated with cytotoxic lymphocytes (T-killers). These bonds have received the name "perforines" and "cytolysins".

It is established, that each T-effector is capable to lyse some foreign cells-targets. This process is carried out in three stages: 1) recognition and contact to cells-targets; 2) lethal blow; 3) lisys cells-targets. Last stage does not demand presence T-effector as it is carried out under influence perforines and cytolysins. In a stage of lethal blow perforines and cytolysins operate on a membrane of a cell-target and form in it pores through which the water which is breaking off cells gets.

Among the humoral factors allocated in the course of the immune answer, it is necessary to specify in the factor of a necrosis of tumours and interferons.

Action of interferons not specific as they possess various functions - is suscitated by activity of K-cages and macrophages, influence immediately DNA - and RNK-CONTAINING viruses, suppressing their growth and activity, detain growth and blast malignant cells.

The humoral immune answer is provided with antibodies, or immunoglobines. At the person distinguish 5 basic classes immunoglobines: IgA, IgG, IgM, IgE, IgD. All of them have as the general, and specific determinants.

Immunoglobines class G. At the person are the most important. Their concentration reaches 9-18 g/l. Immunoglobines this class provide anti-infectious protection, bind toxins, strengthen phagocytic activity, activate complement system, cause agglutination bacteria and viruses, they are capable to pass through a placenta, providing the newborn so-called passive immunity.

Immunoglobines A. Dividev class on 2 versions: serumal and secretory. The first of them are in the blood, the second - in various secrets. According to it serumal immunoglobin And takes part in general, immunity, and secretory provides local immunity, framing a barrier on a way of penetration of infections and toxins to an organism.

The secretory is in external secrets - in a saliva, slime traheobronchial a tree, genitourinary ways, milk. Molecules immunoglobin And, present at internal secrets and liquids, essentially differ from molecules of external secrets. The secretory component, most likely, is formed in epithelial cells and further joins molecule IgA.

IgA will neutralise toxins and causes agglutination microorganisms and viruses. Concentration serumal IgA fluctuates from 1,5 to 4 g/l.

Maintenance IgA sharply increases at diseases of the top respiratory tracts, a pneumonia, infectious diseases of a gastroenteric tract, etc.

Immunoglobines v's class in neutralisation of toxins, opsonization, agglutination and bacteriolisys, carried out by a complement. To this class, for example some natural antibodies also concern foreign erythrocytes. Maintenance IgE raises at infectious diseases at adults and children.

Immunoglobines class D. Represent the antibodies localised in a membrane of plasmocytes, in Serum their concentration is insignificant. Value IgD is not found out yet, assume, that they participate in autoimmune processes.

Immunity regulation

Intensity of the immune answer is in many respects defined by a condition of nervous and endocrine systems. It is established, that the boring of various subcortical structures (a thalamus, a hypothalamus, a grey hillock) can be accompanied both intensifying, and inhibition of immune reaction to introduction of antigens. Excitation of sympathetic department of independent (vegetative) nervous system, as well as adrenaline introduction is shown, that, strengthens a phagocytosis and intensity of the immune answer. Rising of a tonus of parasympathetic department of vegetative nervous system leads to opposite reactions.

Stress, and also depressions oppress immunity that is accompanied not only the raised susceptibility to various diseases, but also frames favorable conditions for development of malignant neoplasms.

For last years it is established, that a pituitary body and an epiphysis by means of special peptides the bioregulators which have received the name "cytomedines", supervise thymus activity. The forward share of a pituitary body is a regulator mainly cellular, and back - humoral immunity.

Immune regulatory system

Recently the assumption that exists not two systems of regulation (nervous and humoral), and three (nervous, humoral and immune) is come out. Immunocompetent cells are capable to interfere with a morphgenesis, and also to regulate a current of physiological functions. Is not subject to doubt, that T-lymphocytes play extremely important role in an angenesis. Numerous researches show, that T-lymphocytes and macrophages carry out "helper" and "supressor" functions concerning an erythrogenesis and a leukopoiesis. Lymphokines and monocytes, allocated with lymphocytes, monocytes and macrophages, are capable to change activity of the central nervous system, cardiovascular system, breath and digestion organs, to regulate contractile functions of a smooth and cross-section-striatal musculation.

Especially important role in regulation of physiological functions belongs to interleukines which are "a family of molecules for all occasions" as interfere with all physiological processes proceeding in an organism.

The immune system is a homeostasis regulator. This function is carried out at the expense of development of the autoantibodies binding active enzymes, factors of coagulation of blood and excess of hormones.

Immunologic reaction, on the one hand, is an integral part humoral as the majority of physiological and biochemical processes is carried out at immediate participation of humoral intermediaries. However quite often immunologic reaction has aim character and by that reminds the nervous. Lymphocytes and monocytes, and also other cells which are taking part in the immune answer, give the humoral intermediary to immediately organ-target. From here the offer to name immunologic regulation is cellular-humoral. The basic role in it should be taken away to the various populations T-lymphocytes, carrying out "helpers" and "suppressors" functions in relation to various physiological processes.

The account of regulatory functions of immune system allows doctors of various specialities to approach to the decision of many problems of clinical medicine in a new fashion.