The observation that PTPN22R619W mice had a similar expansion of Tregs to the PTPN22-KO mice, raises the intriguing possibility that in man, carrying the PTPN22R620W allele might even be protective against secondary autoimmunity following therapeutic Ab depletion, rather than being an increased risk factor as we originally hypothesized. This evidence concerns the gene PTPN22 and Autoimmunity.