Integrated single cell and spatial transcriptomics reveal autoreactive differentiated B cells in joints of early rheumatoid arthritis

Abstract

B cells play a significant role in established Rheumatoid Arthritis (RA). However, it is unclear to what extent differentiated B cells are present in joint tissue already at the onset of disease. Here, we studied synovial biopsies (n = 8) captured from untreated patients at time of diagnosis. 3414 index-sorted B cells underwent RNA sequencing and paired tissue pieces were subjected to spatial transcriptomics (n = 4). We performed extensive bioinformatics analyses to dissect the local B cell composition. Select plasma cell immunoglobulin sequences were expressed as monoclonal antibodies and tested by ELISA. Memory and plasma cells were found irrespective of autoantibody status of the patients. Double negative memory B cells were prominent, but did not display a distinct transcriptional profile. The tissue architecture implicate both local B cell maturation via T cell help and plasma cell survival niches with a strong CXCL12–CXCR4 axis. The immunoglobulin sequence analyses revealed clonality between the memory B and plasma cell pools further supporting local maturation. One of the plasma cell-derived antibodies displayed citrulline autoreactivity, demonstrating local autoreactive plasma cell differentiation in joint biopsies captured from untreated early RA. Hence, plasma cell niches are not a consequence of chronic inflammation, but are already present at the time of diagnosis.

A comprehensive analysis of rheumatoid arthritis B cells reveals the importance of CD11c+vedouble-negative-2 B cells as the major synovial plasma cell precursor

“…A further study of newly diagnosed, untreated RA patients assessed just under 2000 B cells from 3 RA patients, 2 of whom were seronegative for antibodies directed at citrullinated autoantigens (i.e., ACPA -ve ). Here there was no enrichment of ITGAX +ve (encoding CD11c) or CD27 -ve IgD -ve B cells (44). The difference between these observations and our study may relate to the early stage of RA and the limited number of B cells assessed with the predominance of ACPA -ve RA donors in that study.…”

“…Furthermore, having clonal families containing diverse combinations of B cell subsets including both naïve B cells and ASCs suggests that the immunological response is local to the joint and naïve cells are migrating to the joint where they then become activated. This is supported by another single cell sequencing study of rheumatoid synovial B cells, which identified that over 50% of the plasma cells were derived from clonal families that also contained memory B cells (44). DN2 cells express CD11c, that is driven by the expression of the transcription factor T-bet.…”

“…A further study of newly diagnosed, untreated RA patients assessed just under 2000 B cells from 3 RA patients, 2 of whom were seronegative for antibodies directed at citrullinated autoantigens (i.e., ACPA -ve ). Here there was no enrichment of ITGAX +ve (encoding CD11c) and CD27 -ve IgD -ve B cells (44).…”

Heterogeneity of antibody-secreting cells infiltrating autoimmune tissues

“…Autoreactivity of ASCs in RA was also probed with tagged-ACPA, and showed that a subset of CD20 -CD138 + ASCs residing outside EGCs were producing autoantibodies (111). Autoreactivity against ACPA was further confirmed with the recombinant antibody technology (112). These ASCs in RA lesions were probed t be nonsusceptible to rituximab treatment (113).…”

“…Data regarding BAFF-R, TACI and BCMA expression on ASCs at the protein level are missing. However, BCMA and TACI has been described in ASCs from synovial tissues at the mRNA level ( 112 ).…”