Endogenous prostaglandin synthesis and the control of lymphocyte function

Prostaglandins serve an important regulatory role in immune responses. Much of their activity seems to involve regulating the early stages of lymphocyte or macrophage activation. Besides the capacity of prostaglandins to control lymphocyte activation directly by blocking transformation, at least one type, PGE2 can induce a class of glass-adherent T-cells to produce a suppressive peptide in vitro. The data we have obtained suggest the existence of a feedback loop in which PG production by an activated T-cell serves as the signal that induces a second T-cell to release a suppressor peptide. This peptide can then regulate the ability of the activated T-cell to pass through the cell cycle. Other examples of feedback loops have recently been postulated or shown to exist among immunocompetent cells. It remains to be shown how these various regulatory loops combine to form the integrated network that modulates immunoresponsiveness.