Different mechanisms account for the suppression of interleukin 2 production and the suppression of interleukin 2 receptor expression in Trypanosoma brucei-infected mice

Lymph node cell populations derived from Trypanosoma brucei-infected mice failed to produce interleukin 2 (IL 2) in response to a potent mitogenic trigger and suppress the potential of normal lymph node cells to secrete IL 2 in co-culture assays. This suppression is promptly restored by the addition of indomethacin, which blocks prostaglandin synthesis, but is not markedly affected by the addition of catalase, which degrades H2O2. The suppression of the IL 2 receptor expression, on the other hand, is not restored by the addition of indomethacin, nor by the simultaneous supply of both indomethacin and catalase. This discrepancy is not caused by an extreme susceptibility of the receptor expression to low prostaglandin (PG) concentrations, but rather by the presence of suppressive cells that operate through a PG-independent mechanism. This suppressive mechanism accounts for the loss of the IL 2 receptors on both the Ly-2+ and the L3T4+ T cell compartment. The indomethacin-treated co-cultures, which manifest a normal IL 2 production but lack the IL 2 receptors, manifest an impaired DNA synthesis and contain a decreased number of T cell blasts.