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The content of Ig-bearing lymphocytes and their precursors in the mouse bone marrow was investigated 6 and 36 hours after the hydroxyurea treatment. Some increase of the B-cell content takes place in the trated bone marrow. Dividing and non-dividing B-cell precursors, except the stem cells, were practically absent.

The functional activity of natural killers (NK) in the spleen and lymph nodes and interleukin-2 (IL-2) production have been studied in MPL-MpJ-lpr/lpr (H-2k) mice with genetically predetermined autoimmune diseases and CBA (H-2k) mice. In MPL/l mice it has been shown that NK activity in the spleen was markedly depressed already in the first month of life, whereas in lymph nodes there is a substantial NK activity on days 7-10, which reaches its maximum by the second month and by the 6th months is practically intractable. IL-2 production in MPL/l mice was depressed at all stages of investigation.

The immune competence of C57Bl/6 mice implanted with EL-4 lymphoma of Lewis Lung carcinoma 3LL was investigated during 3 weeks after implantation. Splenic lymphocyte responses to mitogens (Con A, PHA, LPS, PWM) cytotoxic T lymphocytes (CTL) and interleukin-2 (IL-2) production were assessed. A dramatic reduction in mitogenic responses to Con A and PHA was observed during tumour progression. LPS and PWM responses were less depressed. Con A-induced IL-2 production correlated with Con A and PHA responses. Allospecific CTL response to mastocytoma P 815 was not decreased in syngeneic tumour-bearing mice.

The effect of the in vivo treatment with synthetic interferon inducer B-58 on natural killer (NK) and cytostatic cell activity was studied in CBA and A/Sn mice. A marked increase in NK cell activity against target cells YAC-1 was observed in the spleen of CBA mice within 4 days after treatment. On the other hand, NK activity in A/Sn mice was not affected by B-58. However, B-58 was shown to enhance cytostatic cell activity both in CBA and A/Sn mice, when tested against target cells P 815.

Natural cytotoxic activity of cells from human fetal spleen, liver, bone marrow, appendix, tonsilar glands and thymus was investigated in 14-26-week-old embryos. The spleen and liver expressed powerful NK activity against K-562 target cells from a 22 week-old embryo. Thymocytes and cells from the appendix and tonsilar glands displayed but negligible cytotoxic activity.

The effect of different antisera to cell surface antigens on EA-rosette formation was investigated. Anti-immunoglobulin serum causes almost total blockade of EA-rosette formation by murine spleen and bone marrow cells. Rabbit anti-mouse brain-associated theta-antigen immunoglobulin has the same effect on EA-rosette formation by murine splenocytes but it has a slight action on EA-rosette formation by rat splenocytes. The mixing of rat splenocytes and autologous or mouse thymocytes increased the blocking influence of anti-BA theta-immunoglobulin. These findings indicate a requirement for specific antigen in the test-system for blockade of EA-rosette formation. This antigen is not necessarily expressed on the surface of Fc-receptor-bearing cells.

Conditions have been established for the effective separation of Fc+ and Fc- cells, using sheep red blood cells monolayer, sensitized with the anti-SRBC antibodies. The method was modified by replacement of poly-L-lysine by protamine sulfate. The electrophoretic distribution profiles of Fc+ and Fc- mouse splenocytes were determined. Fc+ cells had mostly a slow electrophoretic mobility. The Fc- cells were more mobile. The Fc+ fraction contained mainly B-lymphocytes, and the Fc- fraction was enriched with T cells. There was an extensive overlap between the electrophoretic profiles of the Fc+ and Fc- splenocytes. After the splenocyte passage through the glass bead column the overlap became much less.

Con A-induced production of interleukin 2 was studied in peripheral blood lymphocytes obtained from 15 normal subjects and 42 patients with different thyroid diseases. It was found that thyroid diseases are accompanied by changes in IL 2 production. The level of IL 2 production by T lymphocytes is determined by the functional status of thyroid glands, their anatomy, stages of the disease and mode of treatment.

A bacterial adhesion technique for identification of Fc-receptor bearing cells is based on the ability of Staphylococcus aureus, Cowan 1 strain, to form rosettes with cells previously treated with immune complexes or heat aggregated Ig G. The new technique is distinguished from other Fc-receptor detection methods by its simplicity and ease of detection of both immune complexes and aggregated IgG-binding cells.

Interleukin 2 used in vitro and in vivo induces effectively the recovery of cytotoxic activity of natural killers and lectin-dependent cellular cytotoxicity effectors in stress-immobilized CBA mice. This lymphokin can be used for correction of stressor depression in the cells of the natural anti-tumor resistance system.

Mice exposed to immobilization stress manifested a dramatic lowering of the activity of normal killers against YAC-1 tumor as well as against the lectin-induced cellular cytotoxicity mediated by Helix pomatia agglutinin and detected by the cytolytic test against xenogeneic tumor cells K 562. Exposure to stress did not provoke any change in the production of cytotoxic factor of normal killers, whereas dexamethasone (5 X 10(-7) M) in vitro inhibited the production of this factor.