High circulating levels of soluble scavenger receptors (sCD5 and sCD6) in patients with primary Sjogren's syndrome

Objective. To determine the existence of circulating levels of soluble scavenger receptors (sCD5 and sCD6) in patients with primary Sjogren's syndrome (SS), and to analyse the correlation with clinical and immunological features of SS. Methods. Ninety consecutive patients with primary SS were studied. All patients fulfilled four or more of the European diagnostic criteria for SS. sCD5 and sCD6 levels were determined using a specific enzyme-linked immunosorbent assay (ELISA) developed in our laboratory. Results. Detectable levels of sCD5 were found in 39 (43%) SS patients. The mean +/- standard error values of sCD5 were 3.5 +/-0.5 ng/ml for patients with SS and 1.9 +/-0.1 ng/ml for healthy blood donors (P <0.001). We found higher levels of sCD5 in patients with hypocomplementaemia (6.5 vs 3.5 ng/ml, P=0.03) and cryoglobulinaemia (6.9 vs 2.6 ng/ml, P=0.001). On the other hand, detectable levels of sCD6 were found in 60 (67%) SS patients. The mean +/- standard error values of sCD6 were 25.5 +/-7.8 ng/ml in SS patients and 5.27 +/-1.40 ng/ml in healthy blood donors (P=0.01). When the sCD6 levels were compared according to the presence or absence of immunological features, patients with cryoglobulinaemia showed higher levels of circulating sCD6 (77.3 vs 17 ng/ml, P=0.01) than those without cryoglobulinaemia. Conclusion. Patients with primary SS showed higher levels of circulating sCD5 and sCD6 when compared with controls. Moreover, the existence of some immunological features (hypocomplementaemia and cryoglobulinaemia) was associated with high levels of both soluble scavenger receptors. These facts may reflect an enhanced lymphocytic activation in patients with primary SS.