Phosphatidylcholine participates in the interaction between macrophages and lymphocytes

The roleof phosphatidylcholine molecules as mediator for the control oflymphocyte proliferation by macrophages was investigated. Phosphatidylcholine added to the culture medium inhibited the concanavalin A-stimulated lymphocyte proliferation in aconcentration-dependent manner. The potency of this effect wasdependent on the presence of arachidonic acid in thephosphatidylcholine molecules. The phosphatidylcholine transfer frommacrophages to lymphocytes was then investigated. Macrophagesincorporated phosphatidylcholine at a much higher rate than lymphocytesand exported phosphatidylcholine to the culture medium. Whencocultured, a significant amount of phosphatidylcholine incorporated bymacrophages was transferred to lymphocytes. To examine the possiblephysiological importance of the transfer process, the lymphocyteproliferation was measured in coculture conditions. Macrophages weretreated with phosphatidylcholine and washed, and then these cells werecocultured with concanavalin A-stimulated lymphocytes. The effectobserved in coculture was an inhibition of lymphocyte proliferation,which was also dependent on the molecular species of thephosphatidylcholine. Therefore, phosphatidylcholine may act as amediator of the macrophage effect on lymphocyte proliferation.