Tiopronine-induced reduction of rheumatoid factor functional affinity and asialylated IgG in patients with rheumatoid arthritis.

Serum and synovial fluid (SF) from 16 rheumatoid arthritis patients were evaluated before and after a 2-month treatment with tiopronine (TP). The levels of rheumatoid factor (RF) declined, as did the functional affinity of the remaining RF (p less than 0.01 in serum and p less than 0.05 in SF). Concomitant restoration of the sialylation of IgG was observed (p less than 0.05 in serum and SF). Following an initial increase, a significant reduction was observed in the level of soluble interleukin-2 receptors in serum (p less than 0.05) and SF (p less than 0.05) after treatment with TP.