FIGURE 2. IL-21 activates mTORC1 and mTORC2 and suppresses autophagy during Treg differentiation.

Naïve CD4⁺ T cells from SLE and matched healthy control subjects were cultured for 72 hours (or 24 hours to assess LC3 expression) under Treg-polarizing conditions with or without IL-21. (A) Total STAT3 and its phosphorylation at tyrosine 705 (pSTAT3^Y705) were examined by immunoblotting. Representative immunoblot staining of STAT3 and pSTAT3 (left). + and − indicate the presence or absence of IL-21 in the culture media. The signal intensity of pSTAT3 was normalized to that of actin, after which relative pSTAT3 expression to that of IL-21-untreated HC sample was determined. Cumulative data from 5 pairs of matched HC and SLE subjects (right). Data were analyzed by a paired t-test (*p<.0.05, **p<0.01). (B) Phosphorylation of Akt at serine 473 (pAkt) and 4E-BP1 at threonine 37 and 46 (p4E-BP1) as well as LC3 expression was determined by immunoblotting. Representative immunoblot staining of pAkt, p4E-BP1, and LC3 (left). The signal intensity of pAkt and p4E-BP1 was normalized to that of actin, after which relative pAkt and p4E-BP1 expression to that of IL-21-untreated HC sample was determined. The signal intensity of LC3-II relative to that of LC3-I was determined. Cumulative data of pAkt and p4E-BP1 expression and LC3-II/LC3-I ratio from 7, 5, and 9 pairs of matched HC and SLE subjects (right). Results were analyzed by a paired two-tailed t-test (*, p<0.05; **, p<0.01).