Our aim was to study sIL-2R relationship with main serum immunological and LSG immunohistochemical parameters, including surface antigen expression of immune activation, in 27 patients with primary SS. Serum sIL-2R levels were significantly higher in SS (p<0.00005), as well as in SLE (p<0.05) and RA (p< 0.000001) patients than in controls. In SS patients with abnormal slL-2R values (n = 7) we found higher levels of anti-SSB/La antibodies (p<0.05), IgM-RF (p<0.014) and CRP (p<0.003) with respect to those with normal sIL-2R values (n = 20). Moreover, sIL-2R levels correlated positively with those of anti-SSB/La antibodies (p<0.0037) and with CRP (p<0.008). The comparison of groups with (A) and without (B) abnormal slL-2R levels reveals a statistically different percentage of patients with foci number > 1 (86% vs 40%; p <0.047), and CD25 expression on lymphocytes (100% vs 40%; p < 0.008). The frequency (p < 0.025) of CD25 expression on lymphocytes was higher in group A than in group B. The frequency of CD25 expression on the infiltrates correlated not only with sIL-2R levels (p<0.047), but also with anti-SSB/La antibody values (p < 0.044), with Tarpley histological classes (p < 0.009) and with frequency of HLA-DR expression on lymphocytes (p<0.004) and on epithelial cells (p<0.002). The frequency of epithelial CD25 expression also correlated with that of epithelial HLA-DR (p<0.004). Our report suggests that slL-2R is linked to glandular involvement in primary SS.