Mouse macrophages release a neutrophil chemotactic mediator following stimulation by staphylococcal enterotoxin type A

Objective and Design. To examine the role of macrophages in the neutrophil migration induced by staphylococcal enterotoxin type A (SEA) in mice. Materials and Methods: Peritoneal macrophages were harvested from male Swis s mice pre-treated with thioglycollate. After adhering to plastic tissue cu lture dishes, the cells were washed and incubated with RPMI or SEA (0.62-2. 5 mug/ml) and washed again prior to further incubation with RPMI alone. The medium was then collected, sterilized and assayed for promigratory activit y in the mouse peritoneal cavity. Results: Mouse macrophage monolayers stimulated with SEA secreted a thermol abile neutrophil chemotactic component (MNCC-SEA) with a molecular mass > 1 00 kDa (by ultrafiltration). This release was dose- and lime-dependent and was inhibited by dexamethasone but not by indomethacin or BW755C. Dexametha sone, indomethacin, BWA4C, BW755C, BN52021, cimetidine and SR48968 had no e ffect on the neutrophil migration induced by MNCC-SEA while capsaicin and S R140333 reduced this phenomenon. Conclusions: Macrophages play a key role in the neutrophil recruitment indu ced by SEA probably by releasing an MNCC-SEA that presumably induces neutro phil migration via a mechanism mediated by substance P.