IL21 and systemic lupus erythematosus: Third, basophil depletion dramatically dampened both constitutive and PMA-ionomycin-induced IL-21 and IL-4 productions by TFH cells only in the lupus-like context, without significantly influencing their IFNγ or IL-17A production abilities (Fig. 3a–f and Supplementary Fig. 6a–d).