In-vitro T cell mediated function in patients with active rheumatoid arthritis.

In-vitro synthesis of peripheral blood lymphocytes from patients with rheumatoid arthritis was measured after stimulation with phytohaemagglutinin (PHA) in a short-term, serum-free culture system. Diminished responses were found in 16 out of 17 consecutive patients with active disease. Normal PHA responsiveness was recovered by assaying Ficoll-Hypaque isolated E rosette forming cells in serum-free medium, indicating basically normal T cell function in RA. Preincubation of normal peripheral blood lymphocytes (or isolated E rosette forming cells) with sera obtained from patients with active RA for 30 minutes at 4 degrees C or 37 degrees C blocked PHA responsiveness in 34 out of 43 tests. This suggests that serum blocking factors may be responsible for reduced T cell reactivity in RA.