Increased proportion of a CD38 ^high IgD ⁺ B cell subset in peripheral blood is associated with clinical and immunological features in patients with primary Sjögren's syndrome

We investigated the correlation between the increased proportion of peripheral B cell subsets and clinical and immunological features in primary Sjögren's syndrome (pSS). We found that the proportion of CD19 ⁺ B cells was significantly increased in pSS as compared with HC and was correlated with serum IgG levels. Moreover, in vitro IgG production by CD19 ⁺ B cells was significantly increased in pSS and was positively and significantly correlated with serum IgG levels. FACS analysis revealed that the proportions of peripherally CD38 ^high IgD ⁺ B cells and CD38 ^high IgD ⁻ B cells were significantly increased in pSS. In addition, the proportion of CD38 ^high IgD ⁺ B cells positively correlated with ESSDAI scores and serum levels of IgG, anti-Ro/SSA and anti-La/SSB antibodies while that of CD38 ^high IgD ⁻ B cells showed no correlation with these parameters. Our data suggest that increased proportion of CD38 ^high IgD ⁺ B cells in pSS is involved in IgG overproduction including autoantibodies, and correlates with disease progression.