Induction of murine peritoneal macrophage colony-forming cells by peritoneal administration of macrophage inflammatory protein-1 alpha.

Peritoneal injection of thioglycollate medium (TM) to mice results in a dramatic increase in total number of peritoneal macrophages within 48 to 72 hours. Unlike resident macrophages, a fraction (10 to 20%) of these newly arrived young macrophages, designated as macrophage colony-forming cells (M-CFC), are highly proliferative and formed macrophage colonies in vitro in the presence of either macrophage or granulocyte-macrophage colony-stimulating factor (M-CSF or GM-CSF). Using a reverse transcriptase polymerase chain reaction (RT-PCR) technique, peritoneal exudate macrophages (PEM) obtained 2 to 5 days after a single TM injection actively expressed mRNA for recombinant murine macrophage inflammatory protein-1 alpha (rmMIP-1 alpha). Yet none or only a trace amount of mRNA for MIP-1 alpha was detected in normal resident macrophages or PEM obtained 7 days after TM treatment. The effect of rmMIP-1 alpha on the induction of exudate M-CFC was investigated. Multiple intraperitoneal (IP) administration of rmMIP-1 alpha caused a marked increase in the total number of peritoneal M-CFC and macrophages similar to but weaker than the increase in TM-injected mice. The total number of neutrophils, mast cells, and eosinophils also increased, but with different kinetics, following multiple injections of rmMIP-1 alpha. rmMIP-1 alpha alone did not stimulate the proliferation of M-CFC, nor did it potentiate their responsiveness to either rmGM-CSF or recombinant human (rh) M-CSF in vitro. Taken together, our results suggest that MIP-1 alpha released by exudate macrophages is a major chemoattractant responsible for the migration of M-CFC from the circulation to the peritoneal cavity during a TM-induced inflammatory response.