Toussirot, E., Lafforgue, P., Boucraut, J. et al. Rheumatol Int (1994) 13: 175. doi:10.1007/BF00390264
Seronegative spondylarthropathies are disorders with the same predisposing antigen, namely HLA B27, a class I molecule of the HLA system. The mechanisms of the different diseases are unknown, and there is no proof of immune system participation. We have investigated patients with spondylarthropathies in order to search for an immunological component in the pathophysiology of these disorders, by measuring the serum level of two inflammatory cytokines-IL1β and TNFα-by a radioimmunological assay and the serum level of two soluble T cell activation markers-soluble IL2 receptor and soluble CD8-by an enzyme-linked immunosorbent assay. The choice of soluble CD8 can be explained by the strong link between HLA B27 and spondylarthropathies. Our series compared 24 patients to 24 healthy matched controls. A similar IL1β serum level was observed in both groups, while in the patients there was a nonsignificant increase in the TNFα level, a significant decrease in the soluble IL2 receptor level and a significant increase in the soluble CD8 serum level. The normal or moderately increased serum IL1β and TNFα levels in the disease group do not exclued a local role for these cytokines in the synovium or other inflammatory areas. However, we found a higher soluble CD8 serum level in the patient group. Most of these patients were in clinical excerbation of their disease. As the serum level of soluble CD8 is well correlated with T CD8 lymphocyte activation, our data suggest that this lymphocyte subset is stimulated and consequently probably involved in seronegative spondylarthropathies.