PTPRC and rheumatoid arthritis: In view of the fact, that SLFN12 is an interferon inducible gene 22 and that RA/SLE patients usually express a type I interferon signature 21, 49, 50, it is intriguing that T cells express less SLFN12. It is tempting to speculate that reduced levels of SLFN12 are a consequence of lower levels of ct‐CD45 in RA/SLE patient plasma.