Enhancement of in-vitro granulopoiesis and induction of differentiation of M1 cells by a glucocorticoid-dependent factor produced from P388D1 cells

P388D1 cells, a macrophage (M luminal diameter) cell line, cultured after stimulation by lipopolysaccharide (LPS), produced a glucocorticoid (GC)-dependent hemopoietic activity. The activity, when coexistent with hydrocortisone (HCS), increased the number of granulocyte (Gr) colonies 2-3 times more than that formed by CSF alone. HCS scarcely increased the number of Gr colonies stimulated with CSF. We designated this activity as GC-dependent myelopotentiator (GDMP). GDMP activity was partially purified by FPLC using Superose 12 and Mono Q columns. The molecular weight of GDMP was calculated as about 55 kD. GDMP activity was distinct from CSF and interleukin 1 (IL 1) found in the culture supernatant. GDMP was associated with the activity inducing differentiation of myeloleukemic M1 cells in the presence of HCS. The activity inducing differentiation of M1 cells and GDMP activity were absorbed with M1 cells preincubated with HCS, but not by the cells preincubated with medium alone. Thus, HCS may have induced GDMP receptor on M1 cells and the M1 cells were differentiated by GDMP. These results suggest that both normal Gr precursor cells and myeloid leukemic cells are differentiated by GDMP and HCS by the same mechanism.