What do we know about memory B cells in primary Sjögren's syndrome?

Abnormalities of memory B cells seem to be closely involved in the pathogenesis of primary Sjögrens Syndrome (pSS) and its malignant complication, B cell lymphoma. Recent studies on B cells in pSS add to our understanding of the distinct memory B cell subsets in pSS. Reduction of peripheral memory CD27(+) B cells, most strikingly of the CD27(+)IgM(+) subset, may indicate a lack of appropriate censoring mechanisms and incomplete differentiation processes within the ectopic lymphoid tissues in pSS. This ectopically formed lymphoid tissue might protect autoreactive memory B cells from deletion by physiological check-points and, thereby, may contribute to the perpetuation of the disease as well as to an enhanced lymphoma risk. Thus, B cells may be potential targets of direct or indirect treatment in pSS.