Affinity Maturation Drives Epitope Spreading and Generation of Pro-inflammatory Anti-Citrullinated Protein Antibodies in Rheumatoid Arthritis.
Arthritis & rheumatology (Hoboken, N.J.)
OBJECTIVE: Rheumatoid arthritis (RA) is characterized by anti-citrullinated protein antibodies (ACPAs), nevertheless, the origin, specificity, and functional properties of ACPAs remain poorly understood. To characterize the evolution of ACPAs, we sequenced the plasmablast antibody repertoire at serial timepoints in subjects with established RA.METHODS: Blood samples were obtained at up to four timepoints from eight anti-CCP+ individuals with established RA. We single-cell sorted CD19+CD3-IgD-CD14-CD20-CD27+CD38++ plasmablasts and co-stained with citrullinated-peptide tetramers to identify ACPA-expressing plasmablasts. Cell-specific oligonucleotide barcodes were utilized followed by large-scale sequencing and bioinformatic analysis to obtain error-corrected, paired, heavy and light chain antibody gene sequences for each B cell.RESULTS: Bioinformatic analysis revealed 170 persistent plasmablast lineages of which 19% included multiple isotypes. Among IgG- and IgA-expressing plasmablasts, we observed significantly more IgA-expressing persistent lineages compared to IgG (P < 0.01). We identified shared CDR3 sequence motifs across subjects. A subset of lineages comprised of later-timepoint derived members with divergent somatic hypermutations encoded antibodies that bind an expanded set of citrullinated antigens. Further, these recombinant, differentially mutated plasmablast antibodies formed immune complexes that stimulated higher levels of macrophage TNF-alpha production compared to antibodies representing earlier-timepoint, less-mutated lineage members.CONCLUSIONS: Our findings demonstrate that established RA is characterized by a persistent IgA ACPA response that exhibits ongoing affinity maturation. This observation suggests the presence of a persistent mucosal antigen that continually promotes the production of IgA plasmablasts, and their affinity maturation and epitope spreading to generate ACPAs that bind additional citrullinated antigens and more potently stimulate macrophage TNF-alpha production. This article is protected by copyright. All rights reserved.
View details for PubMedID 29927104