CD19 and lymphopenia: However, absolute thymocyte counts were comparable between Ndufs4(-/-) and WT mice (Figure 1D). Importantly, lymphopenia was not observed in CD19+ B cells from Ndufs4(-/-) mice, demonstrating that the dLCK-Cre: Ndufs4(loxp/loxp) model exhibits a selective defect in T cells (Supplementary Figure S2A).