Impaired production of interleukin-2 in peripheral blood of patients with sarcoidosis.

In twelve patients with active sarcoidosis we attempted to explain the nature of reduced release on interleukin-2 (IL-2) and the consequent impairment in lymphoproliferative in vitro responses. The addition of exogenous IL-2 containing supernatants was unable to completely restore the defective uptake of 3H-Thymidine suggesting that an impairment of IL-2 producer cells is not enough to explain the in vitro hyporesponsiveness of sarcoid lymphocytes. We also found a reduced number of precursors of IL-2 responder cells, as defined by peripheral blood lymphocytes bearing Tac determinant following in vitro stimulation with mitogens. The abnormalities of both IL-2 producer cells and precursors of IL-2 responder cells in peripheral blood of patients with sarcoidosis are discussed, stressing the importance of the concept of compartmentalization of T lymphocytes in this disease.