Elevated soluble CD8 antigen and soluble interleukin-2 receptors in the sera of patients with juvenile rheumatoid arthritis.

Activated T lymphocytes release various molecules including soluble CD8 (sCD8) antigen and soluble interleukin-2 receptor (sIL-2R). Elevated serum sCD8 antigen levels have been found in patients with viral infections, certain hematologic malignancies, and rheumatoid arthritis. On the other hand, elevated serum levels of sIL-2R have been found in various diseases including juvenile rheumatoid arthritis (JRA). We measured sCD8 antigen and sIL-2R levels using enzyme-linked immunosorbent assays in the sera of 49 afebrile patients with JRA (systemic 15, polyarticular 16, and pauciarticular 18) and 16 normal children. Disease activity was classified as mild, moderate, and severe. Sera from patients with severe JRA expressed statistically significant higher levels of both sCD8 and sIL-2R, whereas patients with mild disease had the lowest levels. There were no differences in the serum sCD8 and sIL-2R levels between the groups of patients with pauciarticular-, systemic-, and polyarticular-onset disease. Patients who were treated with prednisone had statistically nonsignificant higher serum levels of sCD8 and sIL-2R. A statistically significant positive correlation was found between sCD8 and sIL-2R levels, sCD8 levels and erythrocyte sedimentation rate (ESR), and sIL-2R levels and ESR. Our findings further suggest the presence of activated lymphocytes in patients with JRA and show that sCD8 antigen serum levels correlate with both serum levels of sIL-2R and ESR and thus may represent alternative indicators of disease activity.