The effect of plasma upon lymphocyte response in vitro. Demonstration of a humoral inhibitor in patients with sarcoidosis

Abstract

The role of humoral inhibitors of lymphocyte functions was evaluated in subjects with sarcoidosis. A reproducible system was developed to evaluate the capacity of human plasma samples to support lymphocyte responses in vitro to PHA and to Candida albicans antigen.

There was an unacceptable ten-fold variation in lymphocyte response to PHA among cultures that contained different individual samples of normal plasma. However, when any three normal plasma samples were pooled, the variation was reduced to two-fold. Seven out of twenty-five individual normal plasma samples tested did not support stimulation as well as a pool of plasma.

In contrast, autologous plasma sustained normal lymphocyte stimulation as well as or better than pooled homologous plasma. We tested the ability of plasma from subjects with sarcoidosis to support the stimulation of autologous lymphocytes by PHA and antigen, and compared this response to that obtained when the same lymphocytes were stimulated in cultures that contained pooled normal plasma. Lymphocytes of thirteen out of twenty-six subjects with sarcoidosis did not respond to in vitro stimulation in their own plasma as well as they did when cultured in the pooled plasma of normal subjects. Plasma of fourteen out of twenty-five patients with sarcoidosis caused a significant decrease in the response of normal lymphocytes to PHA, even when added to optimal concentration of pooled normal plasma. We conclude that the plasma of patients with sarcoidosis contains an inhibitor of lymphocyte stimulation.