Influence of serotonin on lymphokine secretion in vitro.

It was found that serotonin can induce the secretion of a chemotactic activity for polymorphonuclear granulocytes and the secretion of charge-changing in in lymphocyte cultures derived from guinea pigs and mice. The serotonin antagonists methysergide, pizotiphen, cyproheptadine and ketanserin inhibited the secretion of the serotonin-elicited factors, whereas the histamine-type 2 antagonist metiamide had no inhibitory effect. Moreover, the production of Concanavalin A-induced lymphokines (migration inhibition factor for macrophages, chemotactic factor for polymorphonuclear granulocytes and for thymocytes, charge-changing lymphokines) was suppressed in the presence of serotonin in the lymphocyte cultures. The fractionation of the supernatants derived from the serotonin-stimulated lymphocytes revealed that serotonin produced an activity with a molecular weight of 40 kDa in the presence of which the Con A-elicited response was completely inhibited. These findings support the regulatory role of serotonin with respect to immune reactions.