Increased IL-21 expression induces granzyme B in peripheral CD5+ B cells as a potential counter-regulatory effect in primary Sjögren's syndrome

Abstract

Recently, we reported elevated proportions of circulating follicular T helper cells and higher levels of interleukin- (IL-) 21 in primary Sjögren's syndrome (pSS). Interaction of invariant natural killer T (iNKT) cells with B cells and granzyme B (GrB) production may be also important in pSS. Thirty-two pSS patients and 24 healthy controls were enrolled in our study. We investigated the expression of intracellular GrB and IL-21 receptor (IL-21R) of CD19+CD5+ and CD19+CD5- B cells; furthermore, we determined the IL-21 expression of iNKT cells as well. We also assessed the proportion of transitional (CD19+CD24highCD38high), mature (CD19+CD24intCD38int) and primarily memory (CD19+CD24highCD38-) B cells. CD5+ but not CD5- B cells showed elevated GrB and IL-21R expression in pSS; additionally IL-21 expression of iNKT cells was also elevated. The ratios of transitional and mature B cells were elevated in pSS, while primarily memory B cell percentages were decreased, which correlated with GrB and IL-21R expression of CD19+ B cells. Our results suggest that enhanced IL-21R expression of CD19+CD5+ B cells and production of IL-21 by iNKT cells may play an important role in the pathogenesis of pSS by regulating CD19+CD5+ B cell functions and increasing GrB production, presumably leading to a counter-regulatory effect in the disease.