Autologous and allogeneic suppressor lymphocyte inhibition of human erythroid colony forming unit proliferation.

: Certain in vitro and in vivo animal studies have supported the concept that lymphocyte-derived microenvironmental factors are important in erythroid proliferation. Considerable controversy has developed regarding the applicability of these concepts to human erythroid proliferation. We, therefore, evaluated the role of lymphocytes on human erythroid colony forming unit (CFUE) proliferation in the plasma clot system. Bone marrow (BM) was obtained from normal donors and cocultured with the following cell populations: a) cultured (6 day) lymphocytes autologous or allogeneic to BM; b) cultured lymphocytes stimulated with conconavalin A (Con A), allogeneic lymphocytes or streptokinase streptodornase (SKSD). In general, unstimulated cultured lymphocytes enhanced CFUE proliferation. In contrast, lymphocytes stimulated with Con A. SKSD, or allogeneic lymphocytes suppressed lymphocyte proliferation. The suppressor cell was concentrated in the T-cell fraction obtained by sheep red blood cell rosetting followed by ficoll-Hypaque centrifugation. Both allogeneic and autologous stimulated T-cells suppressed CFUE. Moreover, supernatants from stimulated lymphocyte cultures suppressed CFUE proliferation although the cell of origin and characteristics of the suppressive factors have not been defined. These data support the concept that lymphocytes may play an important role in modulating the human BM erythroid microenvironment.