Suppressor cell responses in patients with rheumatoid arthritis: the effect of thymosin

Peripheral blood lymphocytes (PBL) from patients with rheumatoid arthritis (RA) and age and sex-matched normal controls were compared in a Concanavalin A (Con A)-induced suppressor cell assay. Suppression induced by pre-incubation with Con A was significantly greater in PBL from RA patients than in PBL from normal controls. Preincubation with thymosin fraction 5, in the absence of Con A, also induced greater suppressor cell activity in PBL from normal controls. Preincubation with Con A and thymosin, simultaneously, induced suppression similar to that seen with Con A alone. These results suggest the presence of an immunoregulatory defect in RA, characterized by an excess of both Con A and thymosin-inducible suppressor cells, that may play a role in disease pathogenesis. The implications of these observations for immunotherapy of rheumatoid arthritis with thymosin are discussed.