Page 1 of 6
Close concept: increase of number of eosinophils
As an independent blood cell the eosinophil was for the first time described by T. W. Jones in 1846. Since then many diseases for which the eosinophilia is a characteristic symptom are revealed. Within the last decade after it became clear that in certain cases the isolated changes of this type of cells can be connected with specific mechanisms, some clinical options were grouped in the defined "eosinophilic syndromes". On the other hand, the eosinophilia was always considered as a characteristic sign of infectious process. In what feature of these cells which are found in a small amount in blood of the person and why increase in their number often is associated with rare diseases? These questions continue to concern hematologists. The physiology of an eosinophil of the person completely is not studied yet. Despite it, it is the best of all to consider an eosinophilia in the light of some known facts of cellular physiology. Therefore, at the characteristic of various diseases proceeding with an eosinophilia in the present chapter a reference to specialized functions of eosinophils from the point of view of their contribution to clinical symptoms is made.
The eosinophilia represents a reasonable biological response of a human body on a stress and an injury; it means that the large number of various influences can cause it. For the clinical physician the interesting challenge is represented by definition on the basis of small differences on degree, but not on quality of a source of observed changes. It gives the chance to choose the corresponding therapy. The purpose of the real discussion is illumination of thin differences and improvement of diagnosis.
Tell about existence of an eosinophilia when the quantity of eosinophils in blood exceeds 350 in 1 mkl (0.35 × 109/l). Normal at adult 3,1% of all leukocytes normal borders for children aged from 4 till 12 flyings make eosinophils slightly above. Blood contains only small part from total number of eosinophils. About 300 mature and unripe eosinophial cells in marrow and from 100 to 300 more — in body tissues are the share of each eosinophil circulating in blood.
Structure and functions of eosinophils
Cellular texture and function. Eosinophils received the name as a result of characteristic coloring of the granules located in cytoplasm. In cytoplasm there are two main components — a kernel and a matrix. The kernel has crystalloid structure, usually considerable electronic density and it surrounds an eosinophilic matrix (fig).
The Granulotsitarny cell (at the left) representing the eosinophil which was implemented into a lung parenchyma at the patient with an eosinophilic syndrome.
The cytoplasmatic kernel and matrix can be distinguished on existence of crystals in kernel particles. The surrounding matrix has an appearance of gentle granular area around crystals.
Life expectancy of an eosinophil in blood varies from 5 to 24 h. In release of eosinophils from marrow the main role is played by β-adrenergic receptors. In the marrow the youngest cell identified as eosinophilic is the eosinophilic promyelocyte. Nature of maturing of an eosinophil is almost identical to nature of maturing of a neutrophil. Modern data showed that lymphocytes can influence products of eosinophils in marrow by means of release of the lymphokines produced by lymphocytes. Specific options of function of eosinophils in system of circulation are described below.
Eosinophils possess more expressed ability to phagocytosis, than neutrophils. However phagocytal reaction of eosinophils is expressed to a lesser extent, than at neutrophils, perhaps, as a result of existence at eosinophils of the person of the corresponding network of receptors. Therefore it is improbable that eosinophils possess a significant role in usual phagocytosis. It is known that eosinophils carry out function of cytotoxic cells killers against some parasites. For example, eosinophils are the main operating cells in the course of antitelozavisimy destruction shistosy at a shistosomiaza. The receptors sensitive to IgG and a human complement located on a surface of eosinophils can carry out start of this cytotoxic reaction.
The substances emitted by eosinophils. Cytotoxic influence on metaphytes and parasites, and also other reactions of allergic type which are carried out by means of eosinophils depend on fixation of the complement for the purpose of recognition. This recognition leads to secretion from granules of peroxidase, a histamine and "the main main protein" (MBR) with which connect cytotoxic effect. Besides, they can cause destruction of surrounding fabrics as a result of "effect of presence".
Eosinophilic modulators. Process thanks to which the eosinophilia becomes a clinical phenomenon, is still studied insufficiently; immediate hypersensitivity or activation of reaction of a complement, apparently, provoke release of eosinophils from marrow. Degranulation of mast cells is important as it leads to release both a histamine, and proteins — an eosinophilic chemotactic factor of an anaphylaxis of ECFA, an eosinophilic chemotactic factor of a complement of ECF-C and the activator of stimulation of eosinophils of ESP. Besides, complexes antigen — an antibody can stimulate release of ESP. Then these factors interact with lymphocytes, causing further release of lymphokines.