Erythropoiesis in vitro: effect of normal versus "transfusion-sensitized" mononuclear cells.

The effects of mononuclear cells from nontransfused and transfused dogs on the growth of erythroid colonies (EC) from DLA-identical littermates were studied. To this purpose, marrow samples were cultured both before and after one to three transfusions from the DLA-identical littermate. Mononuclear cells obtained before transfusions and cocultured with autologous marrow or marrow from DLAidentical littermates significantly increased the number of EC over that obtained in control cultures in 50 of 52 experiments. The magnitude of stimulation observed was dependent upon the ratio of mononuclear cells to EC precursors, suggesting that mononuclear cells interact directly with erythroid colony-forming units in some regulatory capacity. After transfusion, the effect of mononuclear cells on littermate marrow was significantly altered, resulting in most cases either in a failure to increase or an actual decrease in EC numbers. A lesser reduction in EC numbers in a smaller number of dogs was also seen with autologous mononuclear cells after transfusion. The strong reduction of littermate EC by mononuclear cells from most dogs after transfusion is presumably related to an immune reaction against minor tissue antigens, and it suggests that transfusion-induced sensitization must be considered when interpreting the effects of lymphocyte populations on the growth of erythroid colonies.