Production of colony-stimulating activity (CSA) by T-chronic lymphocytic leukemia cells.

T-lymphocytes are probably involved in regulating myelopoiesis. We show that homogeneous populations of leukemic T-lymphocytes freshly obtained from two patients with T cell chronic lymphocytic leukemia produce colony-stimulating activity. The cells from both patients showed the antigenic and biochemical phenotype of the mature T-lymphocyte of the helper subset. This adds further support to the view that helper T-lymphocytes may regulate hematopoiesis in addition to their role in the immune function.