Secretion of monocyte chemoattractant protein-1 (MCP-1) by human mononuclear phagocytes.

Concentrations of MCP-1 and NAP-1 in culture fluids of human leukocytes were measured by sandwich ELISA. PPD caused PBMC's from tuberculin-sensitive subjects to secrete MCP-1 and NAP-1. PPD did not stimulate secretion by cells from a tuberculin-negative subject. Since the amounts secreted were more than could be produced by the few PPD-sensitized lymphocytes in the culture, we postulate that other cells were stimulated to secrete these chemoattractants. This study evaluated secretory capacity of one of the cell types in the PBMC culture. Unstimulated monocytes did not secrete MCP-1 or NAP-1. In order of increasing effect, IL-2 + IFN gamma, IL-1 alpha, and LPS caused monocyte secretion of MCP-1. The rank order for NAP-1 secretion was the same. TNF alpha did not cause secretion of MCP-1, but caused about the same amount of NAP-1 secretion as IL-2 + IFN gamma. Composition of the culture medium was especially critical for LPS-induced secretion of MCP-1, which was greatly enhanced by FCS and by Iscove's DMEM compared to RPMI 1640. IL-4 inhibited LPS-induced secretion of both MCP-1 and NAP-1. Secretory patterns were also a function of mononuclear phagocyte phenotype. LPS-induced secretion of MCP-1 was much greater for monocytes cultured several days in CSF-1 than for freshly isolated monocytes. LPS stimulation of bronchoalveolar macrophages caused NAP-1 secretion, but no secretion of MCP-1 above a relatively low baseline level.