Activated platelets stimulate human neutrophils functions.

Opsonized zymosan is able to induce polymorphonuclear leucocyte activation as reflected by lysosomal degranulation and light emission. However this stimulus is a weak inducer of arachidonic acid metabolism in these cells. We have studied the effects of co-incubation of polymorphonuclear leucocytes and platelets, each of them exposed with its specific stimulus (i.e. opsonized zymosan and thrombin). The granule constituent release was enhanced in the presence of activated platelets, but not the chemiluminescence. The same results were found in time-course experiments. Another important effect of this co-incubation was the potentiation of the synthesis of 5-lipoxygenase metabolites of arachidonic acid by activated platelets. The in vitro study of cellular cooperation may be of great interest in evaluating the role of the messenger processes occurring from one cell to another.