A complex of reactions regulating the number of cells in organs and tissues under normal and pathologic conditions is one of the most important systems of multicellular organisms. In this system, which controls both cell proliferation and clearance, clearance has been given special attention during the last three decades. Some stages of the clearance are known (the choice of "unwanted" cells, their destruction not affecting the surrounding tissue, and, finally, removal of the corpses), and undeniable progress has been achieved in the understanding of the second stage mechanisms, whereas mechanisms of elimination per se of cells or their fragments still continue to be terra incognita. The clearance of such cells is mainly determined by different components of natural and adaptive immunity: phagocytes, complement, opsonins, antigen-presenting cells, etc. Recently specific "danger signals", such as hydrolases, DNA, heat shock proteins, and other potential immunogens released by cells during their elimination have been discovered. Entering the extracellular space, these signals induce inflammation and injury of the surrounding tissues, i.e., autoimmune reactions. Heat shock proteins, in addition to chaperon activity, act as signaling, costimulating, and antigen-carrying molecules in the interactions of dying cells and the immune system.

Growth characteristics of human hemopoietic cells in erythremia and chronic myeloid leukemia were studied using agar cultures with and without hemopoietic growth factors. Agar cultures, similarly to cultures on other semisolid media (plasma clot, methylcellulose) can be used for early differential diagnosis of polycythemia vera (erythremia) and secondary erythrocytosis: erythremia, but not erythrocytosis, is characterized by spontaneous (erythropoietin-independent) formation of colonies from erythrocyte precursor cells. Spontaneous colony formation from granulocyte-macrophage precursor cells can serve as an important test for early diagnosis of chronic myeloid leukemia. The study of colony formation from granulocyte-macrophage precursors and of the capacity of bone marrow cells to form colonies from hemopoietic stromal precursor cells revealed new characteristics of the studied myeloproliferative diseases. Presumably, spontaneous colony formation from erythrocytic and myeloid precursors should be regarded as a sign of tumor transformation of the studied hemopoietic cells.

Exposure of cultured cells and small animals to ionizing radiation as well as irradiation of cultured cells with He-Ne laser can cause changes in the functional condition of plasma membranes. The ionizing radiation-induced cell membrane alterations have been determined after either partial or local exposures. The aim of the present study was to reveal whether the local laser treatments cause a general, distant, so called abscopal" effect measured at cellular level, when the laser treatment is intended as a stimulatory procedure. The biological effect of infrared laser (mean power of 5 Watts, 150 Hz frequency, 890 nm wavelength) was demonstrated through 3H-concanavalin A binding by blood cells of daily irradiated (altogether 10 exposures) oncological and non-oncological patients as well as by changes in the proliferation of bone marrow cells of whole body gamma-irradiated (4 Gy) rats, partially laser-treated. The lectin binding of lymphocytes of oncological, as well as ischaemic heart disease patients was increased immediately after the first laser treatment. However, it was decreased after completion of the full course. In cases of inflammatory diseases the test parameters were either unchanged or decreased as compared to their self-control values. The platelets and erythrocytes did not react in any group. Gamma irradiation caused a deep inhibition of proliferation of rat bone marrow cells. The number of fibroblast colony-forming units (CFU-F) could be increased again if the animals were partially exposed to laser. Laser irradiation of one of the femurs led to some recovery of CFU-F values in the exposed as well as unexposed femur. Thus, local infrared laser treatment induces abscopal effects on the cell membrane and cell proliferation characteristics.