Leukolysis

LEUKOLYSIS (syn. leukocytolysis), the dissolution and breakdown of leukocytes. As a physiological phenomenon, leukolysis serves as an expression of the normal death of leukocytes, whereas as a pathological phenomenon it occurs under conditions leading to the destruction and breakdown of leukocytes (leukolysis from leukocytolytic serum; leukolysis before the critical drop in temperature in infections, e.g., in croupous pneumonia; as the initial, fleeting phase of the leukocyte reaction followed by leukocytosis; leukolysis from the injection of toxic substances into the blood; leukolysis under the influence of X-irradiation; locally in the abdominal cavity, as a result of introducing into it even such indifferent substances as broth used for growing bacteria or a physiological solution, in which latter case it is more often called phagolysis). Leukolysis leads to temporary leukopenia, but one cannot draw the reverse conclusion from this; in other words, by no means every leukopenia is caused by leukolysis (leukopenia in peripheral vessels as a result of a disturbance in the distribution of leukocytes, their accumulation in deeper parts of the organism and mainly in the capillaries of the lesser circulation; leukopenia from the depressive effect of a given factor on the hematopoietic function of the bone marrow). Leukotoxic or leukocytolytic serum, administered parenterally, produces leukolysis through a direct effect on leukocytes in the blood, as does a large dose of X-rays when irradiating various parts of the body periphery; in most other cases, artificially induced leukolysis is accomplished indirectly through the spleen, which secretes a special substance that dissolves leukocytes (see Leukocytolysin). Morphological criteria of leukolysis in the stage preceding the complete dissolution of leukocytes are degenerative forms of the latter, either forms with dark, pyknotic nuclei or, conversely, with pale, as if "eluted" or swollen nuclei and vacuolated protoplasm. On preparations made by smearing on a glass slide, the picture of complete destruction of leukocytes is most often obtained ("nuclear shadows"). The question of the significance of leukolysis for the organism is of interest. Mechnikov once reduced all of the organism's struggle against infection to phagocytosis. But as early as 1892, S.S. Botkin drew attention to leukolysis as a factor "playing a paramount role in the self-defense of the organism," greater even than phagocytosis. Leukocytosis in Botkin's experiments, both with the injection of tuberculin and with the immunization of horses against tetanus toxin, was subsequently replaced by leukolysis, and this moment coincided with the critical drop in temperature. The same was noted by Botkin in fibrinous pneumonia. Later, E.S. Botkin became interested in this phenomenon, to whom the very term leukolysis belongs, and especially I.I. Manukhin. According to the doctrine put forward by them, the organism's struggle against the infectious agent boils down mainly to leukolysis: this is the first stage preceding leukocytosis and the concluding stage when, at the end of the disease, leukocytes already loaded with antibodies break down, and Manukhin even proposed a special method for aborting infectious diseases through leukolysis artificially induced by the action of small doses of X-rays on the spleen (see Leukocytolysin). A critique of this doctrine is given in the works of G.P. Sakharov and boils down essentially to two propositions: 1) initial leukolysis for the most part cannot be of essential significance, given that leukocytes often do not contain substances harmful to a given species of microbes, and 2) concluding leukolysis, although undoubtedly a powerful weapon in the organism's struggle against infection, can hardly play a decisive role in that regard, since antibodies can freely pass into the blood even without the participation of leukocytes.