Independent regulation of myeloid cell growth and differentiation inducing proteins: in vivo regulation by compounds that induce inflammation.

Regulation of the in vivo production of myeloid cell growth-inducing (MGI-1) and differentiation-inducing (MGI-2) proteins has been studied in mice injected with the inflammation-inducing compounds sodium caseinate, thioglycollate and bacterial lipopolysaccharide. The results indicate that these inflammation-inducing compounds can induce in vivo production of MGI-1 and MGI-2; that different inducing agents can cause a different body-distribution of MGI-1 and MGI-2; that there is an independent regulation of in vivo production and distribution of MGI-1 and MGI-2; and that there is a granulocyte growth-inducing protein (MGI-IG = G-CSF) that is not identical to the differentiation-inducing protein (MGI-2). Resident peritoneal macrophages produce MGI-1 and MGI-2 in vitro, but inflammatory macrophages show a reduced ability to spontaneously produce these proteins after in vivo injection of caseinate or thioglycollate. The results thus also indicate that macrophage activation can affect the ability of macrophages to produce the myeloid cell regulatory proteins MGI-1 and MGI-2.