FCRL4 and rheumatoid arthritis: In this study, we found differences in FcRL family member expression between SF ABCs and those from PB: FcRL3 and FcRL5 are decreased in SF ABCs, but FcRL4 is increased, in agreement with the observation that SF CD21−/low B cells from RA SF have increased FcRL4 expression compared to their PB counterparts [9].