PBX1 and systemic lupus erythematosus: We have proposed a model for the genes involved in lupus pathogenesis with a first group of genes breaking tolerance, such as Ly108 in Sle1b (23), a second group amplifying/ polarizing autoimmune activation, such as Pbx1 in Sle1a (24), and a third group of genes modulating disease severity in target organs, such as the kallycrein gene family in Sle3 (25) in the NZM2410 lupus model (26).