Clonal characteristics of paired infiltrating and circulating B lymphocyte repertoire in patients with primary biliary cholangitis

Background PBC is a prototypical autoimmune liver disease characterized by portal lymphoplasmacyte infiltration. ALD is a prototypical environment-driven disease, featured by mild lymphocyte infiltration. We hypothesize B cells are more involved in the pathogenesis of PBC. By analyzing the infiltrating B cell repertoire, we aimed to unveil greater oligoclonal expansion and active clonal exchange between liver and periphery in PBC than in ALD patients. Methods Using NGS of Ig H chain genes, we analyzed the liver-infiltrating and paired peripheral B lymphocyte repertoire from 9 PBC and 4 ALD patients. Results In the liver of PBC and ALD patients, (1) roughly 10% of the B lymphocytes were clonally related and highly expressed, and there were also lineages that underwent extensive clonal expansion; (2) there was different use of IGHV/IGHJ segments between PBC and ALD, suggesting distinct Ag exposure backgrounds, but this did not lead to a significant difference in their clonal expansion level. Analysis of data sets from paired samples further revealed, (3) direct clonal exchange and evolutionally-related B cell clones between the infiltrating and peripheral repertoire; (4) the seeding of the infiltrating clones to periphery, and peripheral ones to the liver, for further extensive evolution. Conclusions The oligoclonally expanded nature of the infiltrating B cell repertoire implies B cell immunity is involved in the pathogenesis of both diseases. The observed clonal exchange might provide an approach to identify and monitor the infiltrating B cells through the periphery. This article is protected by copyright. All rights reserved