High-Throughput Single-Cell Analysis of B Cell Receptor Usage among Autoantigen-Specific Plasma Cells in Celiac Disease.

Characterization of Ag-specific BCR repertoires is essential for understanding disease mechanisms involving humoral immunity. This is optimally done by interrogation of paired H chain V region (V) and L chain V region (V) sequences of individual and Ag-specific B cells. By applying single-cell high-throughput sequencing on gut lesion plasma cells (PCs)， we have analyzed the transglutaminase 2 (TG2)-specific V:V autoantibody repertoire of celiac disease (CD) patients. Autoantibodies against TG2 are a hallmark of CD， and anti-TG2 IgA-producing gut PCs accumulate in patients upon gluten ingestion. Altogether， we analyzed paired V and V sequences of 1482 TG2-specific and 1421 non-TG2-specific gut PCs from 10 CD patients. Among TG2-specific PCs， we observed a striking bias in and gene usage， as well as pairing preferences with a particular presence of the pair. Selective and biased V:V pairing was particularly evident among expanded clones. In general， TG2-specific PCs had lower numbers of mutations both in V and V genes than in non-TG2-specific PCs. TG2-specific PCs using had particularly few mutations. Importantly， V segments paired with displayed proportionally low mutation numbers， suggesting that the low mutation rate among PCs is dictated by the BCR specificity. Finally， we observed selective amino acid changes in V and V and striking CDR3 length and J segment selection among TG2-specific pairs. Hence this study reveals features of a disease- and Ag-specific autoantibody repertoire with preferred V:V usage and pairings， limited mutations， clonal dominance， and selection of particular CDR3 sequences.