Comparison of immunoglobulin heavy chain rearrangements between peripheral and glandular B cells in a patient with primary Sjögren's syndrome

Abstract

Myoepithelial sialadenitis (MESA) of the major salivary glands is a characteristic feature of primary Sjögren's syndrome (pSS). To delineate systemic and organ-specific influences on B cells in a patient with pSS and benign MESA, individual B cells were simultaneously obtained from the peripheral blood and inflamed parotid gland. Immunoglobulin variable heavy chain (VH) rearrangements in single sorted CD19+ B cells were subsequently amplified, sequenced and analysed. Despite the presence of two clonal expansions using VH1-08 and VH2-70 segments, respectively, the majority of glandular B cells were polyclonal, resembling the VH gene usage and mutational pattern of the corresponding blood population. However, striking differences were observed in the proportion of cells expressing mutated VH rearrangements (blood, 28.9% versus parotid, 80.4%; P < 0.0001). Moreover, the glandular productive VH rearrangements differed significantly from their blood counterparts by a higher mutational frequency (P < 0.0001), shorter CDR3 lengths (P = 0.001) and a less frequent usage of JH6 (P = 0.0292), indicating an accumulation of memory B cells in the inflamed parotid. Thus, both preferential influx/homing of memory B cells and local proliferation may contribute to the pattern of benign MESA in pSS. Notably, one of the glandular clonal rearrangements (using VH1-08) was also detected in the patient's peripheral repertoire.