PTPN11 and Autoimmunity: - both under- and overactivities of disparate Ras effectors - both increased and decreased Ras activities may be implicated in lupus-like autoimmunity - linkage of a susceptibility gene for SLE to 12q24, a locus encompassing PTPN11, encoding SHP-2 SHP-2 inhibits NK cells activation, cytolytic activity and IFN-γ