In vitro migratory response of rat peritoneal macrophages and mast cells towards chemotactic factors and growth factors.

In order to elucidate the mechanisms of mast cell accumulation at tissue sites, mast cell-containing and -depleted rat peritoneal exudates were tested for their migratory ability in the in vitro microdroplet assay. In some experiments, peritoneal cells from ascaris sensitized rats and immature, cultured mast cells were studied as well. Mature mast cells never responded to any stimulus tested, and immature cells exhibited far less responsiveness than their precursors. Macrophages migrated towards LTB4, PAF, formylated peptide, activated and sensitized serum, spleen cell supernatants and less so towards fibronectin, growth factors (EGF, FGF) and growth factor containing media. In general, cells from sensitized animals and young elicited cells were more active than resting macrophages. The data suggest that increased numbers of mast cells at tissue sites are due to in situ maturation of immigrated, macrophage-like precursors.