CD4 and systemic lupus erythematosus: Thus, rapamycin increased ATP production in CD8+ but not CD4+ T cells of B6.TC/Rab4AQ72L mice (Fig. 4D), indicating that rapamycin selectively enhanced the mitochondrial metabolic fitness of CD8+ T cells of lupus-prone B6.TC/Rab4AQ72L mice (Fig. 4D).