CD127lowCD25hi (surface-defined Tregs) vs. CD127hiCD25low CD4+ T cell populations in mutation carrier 5 (SLE) segregated with intracellular FoxP3 positivity, non-discrepant with two unrelated healthy donors (Fig. 4b), in keeping with literature on Treg surface phenotyping [40, 41]. Here, CD4 is linked to systemic lupus erythematosus.