The ability of human monoclonal IgG 1 to accelerate the clearance of rhesus-positive erythrocytes in rhesus-negative volunteers does not correlate with their immunosuppressive effect. Monoclonal antibodies G-17 weakly accelerated the clearance, but decreased the incidence of sensitization, while G-7 and G-12 antobodies eliminated 80-100% erythrocytes for 7 days, and used in combination, these antibodies eliminated all erythrocytes within 3 days. G-7 antibodies stimulated immune response in all doses, while G-12 antibodies stimulated antirhesus response in a dose of 600 pg and notably decreased it in a dose of 1200-1800 ~tg.Key Words: rhesus sensitization; monoclonal anti-rhesus antibodies," erythrocyte clearance," flow cytometryInjections of anti-rhesus immunoglobulin to a rhesusnegative (Rh) woman within 3 days after delivery of a rhesus-positive (Rh +) child 5-10-fold decreases the probability of rhesus sensitization and newborn hemolytic disease in subsequent pregnancies [3,8]. The mechanism of prevention of immunization with passive anti-Rh antibodies is unclear. It is believed that the preventive effect depends on the rate of elimination of Rh + erythrocytes (ER) from the circulation and their destruction in the spleen. Experimental findings indicate that immune response can be effectively suppressed only when the dose of anti-Rh immunoglobulin is sufficient for ER clearance within 5-8 days [5]. Anti-Rh are virtually unavailable, and we investigated the possibility of using monoclonal antibodies (MAb) and established criteria for their evaluation,

Livers from 17to 20-day CBA mouse embryos were maintained for three weeks in organ culture. During this period, hematopoiesis continued; morphologically recognizable cells were identified until day 24 and hematopoietic cells with colony forming ability were present until day 23. The method appears to hold promise for studies of hematopoietic differentiation in vitro.

Treatment of prolonged bone marrow cultures with leukemia inhibitory factor during the first 2 weeks after explantation has no appreciable effect on the production of precursors and mature hemopoietic ceils during 4 weeks of culturing. However, the proliferative potential of polypotent hemopoietic precursors in these cultures increases substantially. The addition of exogenous cytokine has a pronounced effect on the hemopoietic stroma, specifically, on the content of osteogenic precursors and ceils transporting the hemopoietic microenvironment to prolonged bone marrow cultures treated by leukemia inhibitory factor. This effect is confirmed by formation of ectopic hemopoietic foci in vivo, being 2-3 times higher than in the control.

We studied hemopoiesis in mice deficient by the tumor necrosis factor gene. The total number of cells in long-term bone marrow cultures from these mice 2-fold surpassed that in wild-type and tumor necrosis factor p55 receptor-deficient animals. Increased cell production was related to the absence of tumor necrosis factor expression by hemopoietic precursors. The total cell production by explanted hemopoietic cells from tumor necrosis factor-deficient mice did not depend on the genotype of irradiated stromal sublayer in long-term cell cultures from wild-type mice and animals deficient by tumor necrosis factor or p55 receptor. These results suggest that tumor necrosis factor, but not its p55 receptor, is involved in transduction of signals regulating production of cultured cells. Tumor necrosis factor probably regulates hemopoiesis in long-term bone marrow cultures by initiating apoptosis of hemopoietic cells or inhibiting cell proliferation. Increased cell production probably attests to the absence of one or both effects.