FCRL5 and systemic lupus erythematosus: Gene set variation and enrichment analysis revealed a strong enrichment of a previously described B cell signature of IgD–CD27–CXCR5– ‘atypical’ Bm cells from patients with systemic lupus erythematosus (SLE)36, in our SARS-CoV-2-specific CD21–CD27–FcRL5+ Bm cell subset (Fig. 5e,f).