PTPN22 and myeloid sarcoma: Most of PTPs that are highly modulated in secondary MS patients or in MOG-induced EAE mice have been linked with inflammatory processes [27] (e.g. Ptpn22, CD45, PAC-1) but none of these proteins has been associated with OL signaling except Ptprr/PTP-SL, which has recently been shown to be a potential negative regulator of OL differentiation [26], and Ptpn6/SHP-1 a positive regulator [67].