A study of immunomodulating action of mouse alpha/beta interferon (IFN) was performed in conditions of congenital and experimental thymus-dependent immune deficiency. The action of IFN was assessed in vivo, with IFN injected intraperitoneally. It was shown that IFN did not change killer effect of lymphocytes in the reaction of stem cell inactivation in "nude" mice, but enhanced antibody and rosette formation in the spleen of these animals. In addition, IFN did not change these parameters in the spleen of HRS mice with abnormal differentiation of T lymphocytes, but enhanced antibody and rosette formation in the spleen of mice, thymectomized in old age. It is concluded that the normal function of T-system is essential for the action of IFN.

The protective ability and graft-versus-host (GVH) activity in parental strain hematopoietic fetal liver cells (FLC) transplanted to irradiated F1 hybrids were evaluated quantitatively. A 21-day survival of more than 80% of semi-syngeneic mouse recipients required the injection of 2-5 X 10(6) nucleated fetal liver cells (FLC). The same effect could be obtained with FLC cultivated for 4-15 days. 5 to 25 X 10(6) parental FLC were necessary to induce a considerable GVH mortality within 2-3 months after transplantation. Thus, the minimal cell doses of both native and cultivated FLC enough for the maximal protective effect have proved ineffective for the provocation of the fetal GVH disease. Hematopoietic cells from long-term FLC cultures had a low protective potential though they could contain high CFUs concentration. This discrepancy shows clearly that such polypotent precursors as CFUs have no ability to restore hematopoiesis, in other words they cannot be totipotent stem cells.

A case of a primary malignant mesenchymoma of the lung with elements of rhabdomyo-, leiomyo-, osteo-, fibro- and lipo-sarcoma is described. The tumor developed in a man of 58 with a long history of smoking, complaints of chest pains and cough with scanty sputum expectoration. The neoplastic process involved the upper lobe of the left lung and microscopically contained smooth muscle, endothelial, fibroblast-like cells, multinuclear giant cells resembling osteoclasts, strips of osteoid-like hyalinized connective tissue. Electron-microscopic examination revealed myoid-type cells with clusters of myofilaments and Z-type material, cells resembling fibroblasts, osteoclasts and lipocytes. It is suggested that there should be a common histogenesis of primary lung sarcomas arising from a stem cell precursor of mesenchymal origin in lung stroma, bronchial and vascular walls, pleura.

As it is previously shown (Tsyrlova et al., 1986), the level of humoral immune response is not only determined by the reaction of peripheral lymphoid system on antigenic effect, but also is bound up with the observed stem blood cell (SBC) proliferation in bone marrow (Frindel et al., 1976, Kozlov et al., 1982). Dynamics of label accumulation in bone marrow was examined when injecting antigen--sheep red blood cells labeled by radioisotope 51Cr, 125I. The peak of label accumulation in bone marrow, accompanied by the increase in proliferative SBC, was observed on the 3rd day after antigen injection. Furthermore in the course of immunization 51Cr labeled macrophage assortment was changed in time in such a way that a greater number of macrophages was accumulated in bone marrow on the 3rd and 4th days in the immunized animals in comparison with the intact ones. The macrophages in bone marrow are likely to take part in antigen uptake and to mediate its effect on SBC proliferation.

The content of haemopoietic stem cells in mice at the stage of the enhanced radioresistance (day 12 after irradiation with a sublethal dose of 2.75 Gy) was lower than that in the controls. Their repopulation in the repeatedly exposed mice was more intensive than in the intact mice irradiated with the same dose. The authors discuss the significance of the peculiarities observed in understanding the causes of the increase in radioresistance after sublethal irradiation.

After a single or three-fold whole body irradiation of mice with a dose of 4 Gy and the time interval for the proliferation to be restored (5 days or 3 weeks) the survival curve for stem cells of small intestine epithelium with regard to radiation dose was the same as that for non-preirradiated mice. This indicated that the proliferative potential of stem cells in these experimental conditions was not reduced.

In experiments on CBA and BALB/c male mice (3 months of age) and F1(CBA X C57BL/6) hybrids (at the age of 3, 12, and 24 months) a difference was noted in the radiosensitivity of spermatogenic epithelium stem cells displayed by the changes in their colony-forming ability in testicular tubules 42 days following local 60Co-gamma-irradiation. The older the hybrid mice the smaller was the number of spermatogenic epithelium stem cells.

Techniques of clonogenic cultivation with the application of xenogenous feeder (rabbit irradiated bone marrow) were used to study a number of bone marrow colony-forming cells (CFU-F) in 70 patients. A significant increase of CFU-F is observed in chronic myelocytic leukemia and in hepatosplenomegalies of non-leukemic origin CFU-F decreases considerably in the cases of myelofibrosis. Trypsinisation of the bone marrow taken from the cases of myelofibrosis results in a sharp CFU-F increase.

Two types of CFU-s different in the size of their colonies have been found in the liver of 14 day old mice embryo. Statistic processing of the data allowed to prove that large spleen colonies are formed directly by CFU-s, whereas small colonies are formed by pre-CFU-s which undergo preliminary proliferation and only the stochastically differentiate into CFU-s. Approximate concentration of pre-CFU-s constitutes 2.67 per 10(5) embryo liver cells.

Epidermal growth factor (12 ng per 1 g of body mass) and insulin (0.004 units per 1 g of body mass) were introduced into X-ray irradiated (1.8, 2.12, 2.7 Cr) mice. Four hours later bone marrow was extracted from femurs to be introduced into syngenic lethally irradiated recipients. On the 11th day after transplantation the number of exogenic spleen colonies was computed. The epidermal growth factor, in combination with insulin, stimulates in the organism the restoration of hemopoietic colony-forming cells after radiation injury.

Data are presented on histochemical determination of lectin receptors on surface membranes of different haematopoietic and lymphoid cells of healthy persons and of patients with leukemias and lymphomas.