RAB4A and systemic lupus erythematosus: To determine its causative involvement in disease pathogenesis, we replaced the wild-type Rab4A alleles in C57Bl/6 (B6) and lupus-prone B6 SLE123 triple congenic (B6.TC) mice with constitutively active Rab4AQ72L alleles surrounded by loxP sites (B6/Rab4AQ72L; Figures S1A, B, and C).