The growth factor IL-7 induces expression of a transformation-associated antigen in normal pre-B cells.

The B lineage antigen 6C3Ag is expressed by a number of cell types involved in lymphopoiesis. We have investigated whether there is a relationship between activation of normal pre-B cells by the growth factor IL-7 and the expression of 6C3Ag. Sorted sub-populations of bone marrow pre-B cells were cultured with IL-7 and their expression of surface antigens measured. There is a rapid induction of 6C3Ag expression after exposure to IL-7 by pre-B cells but not mature B cells. In particular, the 6C3lo pre-B cells respond very strongly by increasing 6C3Ag expression. The expression of 6C3Ag coincides with increased DNA synthesis and formation of lymphoblasts by the responding cells. The responses seen were specific to IL-7, and to a lesser degree IL-4. We conclude from this that IL-7 specifically induces the expression of 6C3Ag.