In vitro effects of thymopentin on the gamma-interferon production by peripheral blood mononuclear cells from normal subjects and from patients with rheumatoid arthritis.

The in vitro production of gamma-interferon (gamma-IFN) by peripheral blood mononuclear cells (MNC) was measured using a specific radioimmunoassay in 16 patients presenting with active rheumatoid arthritis (RA), in 14 patients with inactive disease, and in 36 control subjects (CS). Unstimulated cultures produced undetectable levels of gamma-IFN and did not incorporate tritiated thymidine. In response to phytohemagglutinin (PHA) 0.2 microgram/ml, MNC from active RA produced 9 times less, and under PHA 2.5 micrograms/ml, 4 times less gamma-IFN than did MNC from inactive RA or from CS. The uptake of tritiated thymidine was, however, similar in the 3 groups. In unstimulated cultures of the 3 groups, thymopentin (TP-5), at all concentrations tested, did not influence either the levels of gamma-IFN or the uptake of tritiated thymidine. In the presence of PHA 0.2 microgram/ml and TP-5, lambda-IFN levels were increased in CS, unchanged in inactive RA and reduced in active RA, whereas no changes were observed in the uptake of tritiated thymidine. Our results show that under our experimental conditions, TP-5 was able to increase the levels of gamma-IFN produced by normal MNC in vitro, but could not reverse the profound defect observed in active RA.