Regulation of lymphoid colony growth by factors derived from human bone marrow

We have previously demonstrated the ability of soluble factors derived from cultured murine and human bone marrow supernatants to modulate a variety of lymphoid functions, including DNA synthesis. In the present report, we show that human marrow supernatants contain a suppressor factor (BSF) that suppresses T-lymphoid colony formation, and an augmenting factor (BEF) that enhances T-colony growth. BSF suppression exhibits no tissue specificity, affecting marrow-derived and peripheral T colonies similarly. The suppressive activity occurs prior to mitogenic activation by TCGF. In contrast, a preferential augmentation of the size and number of marrow-derived T-cell colonies, as compared to peripheral T-cell colonies, was observed in the presence of BEF. BEF required prior mitogen activation of the colony inocula to effect colony enhancement. In addition, the response to BEF was greater for E- than for E+ colony-forming cells, indicating the target of BEF activity to be an early T cell. The active subfraction of BEF with colony-enhancing activity was found to be between 8000 and 30,000 daltons.