THE POTENTIAL ROLE OF THE MACROPHAGE-COLONY-STIMULATING FACTOR, CSF-1, IN INFLAMMATORY RESPONSES - CHARACTERIZATION OF MACROPHAGE CYTOKINE GENE-EXPRESSION

In this report we report that recombinant human monocyte-macrophage colony-stimulating factor-1 (CSF-1) induces resident murine peritoneal cells (PCs) to transcribe several inflammatory cytokine genes, including interleukin (IL)-1 alpha, IL-1 beta, IL-6, and granulocyte-macrophage CSF in a dose-dependent and time-related manner, Peak mRNA levels were seen between 4 and 6 h, CSF-1 did not modulate the expression of tumor necrosis factor-alpha mRNA. The serum content of the culture medium appeared to regulate both the extent of CSF-1-induced gene transcription and the adherence properties of the cells, Decreasing the serum concentration significantly reduced CSF-1-induced transcription and was associated with the rapid spreading of the majority of the adherent cells, This reduced sensitivity to CSF-1 was paralleled by a markedly lower levels of c-fms mRNA encoding the CSF-1 receptor, Induced gene transcription was followed by the release of large quantities of Il-6 only. IL-1 activity remained associated with the cells, Neither supernatant nor cell lysate granulocyte-macrophage CSF activity was inducible above the low levels associated with control cultures, Evidence that the mononuclear phagocytes, as opposed to B or T cells, were the targets of CSF-1 was obtained in two ways: (1) PCs from B6 scid/scid and NOD scid/scid mice consisting of 78-86% MAC-1(+), F4/80(+) cells and few B or T cells, as shown by flow cytometry analysis, released 5- to 10-fold more IL-6 in response to CSF-1 stimulation than B6 PCs, which contained =30% double-positive cells, and (2) pretreatment of B6 PCs with antibodies to the CSF-1 receptor blocked the CSF-1-induced secretion of IL-6. These data suggest that CSF-1 primes noninflammatory mononuclear phagocytes for a role in inflammatory responses but does not provide the necessary signals for either secretion or translation of all cytokines equally.