Soluble CD4 (sCD4) and sCD8 were measured in the sera of 19 patients with active polymyalgia rheumatica (PMR).
We correlated the results obtained with lymphocyte subpopulations, soluble interleukin 2 receptors (sIL-2R), and clinical and laboratory variables at diagnosis. In addition 15 patients were prospectively studied during a 6 month period of prednisone therapy. Assays of the sCD4 and sCD8 molecules and of the sIL-2R were performed using an enzyme-linked immunosorbent kit.
Serum sCD8 and sIL-2R levels were significantly elevated in patients with active disease compared to normal controls, while serum sCD4 and the relative percentage of CD8+ T cell levels decreased. In the 15 patients prospectively studied sCD8 levels fell significantly after 1 week of therapy along with the remission of clinical disease and normalization of erythrocyte sedimentation rate. At the end of the study period, sCD8 values did not differ from normal controls and they were significantly reduced compared to baseline values. CD8+ lymphopenia persisted at the end of the study. sCD4 levels remained significantly lower during the study period. sIL-2R levels fell significantly at the end of the study period. However, the 6-month levels of sIL-2R remained significantly higher compared to controls.
The rise of serum sCD8 levels observed in patients with PMR with active disease suggests an early activation of CD8 T cells. The therapeutic effect of steroid in PMR may be partially mediated by its effect on CD8 activated cells.