Since patients with RA and SLE show altered frequencies in the IgM+ mBc and CD27- mBc subpopulations [24], [25], [27], in which RV-mBc are enriched, we compared the relative frequencies of total and RV-Bc subsets in healthy adult volunteers (HV) and patients prior RTX treatment (prior-RTX) by flow cytometry (see analysis strategy in Figure S1A). Here, CD27 is linked to rheumatoid arthritis.