Regulation and role of different macrophage‐ and granulocyte‐inducing proteins in normal and leukemic myeloid cells

AbstractIt has previously been shown that there are different molecular forms of macrophage‐ and granulocyte‐inducing (MGI) proteins; one form, MGI‐I, induced the formation of colonies with differentiated cells from normal myeloblasts and another form, MGI‐2, induced normal differentiation in MGI+D+ leukemic myeloblasts that no longer require MGI‐I to form colonies. The present results indicate that MGI‐2 can also induce differentiation (without inducing colony formation) in the normal cells, and that MGI‐I induced MIG‐2 in the normal but not in the leukemic cells. It is suggested from these results that MGI‐2 is the differentiation‐inducing protein for normal and leukemic cells whereas MGI‐I is the growth‐inducing protein that induces colony formation by the normal cells, and that induction of differentiation in the normal cell colonies is due to induction of MGI‐2 by MGI‐I.