IL17A and psoriasis: Several studies described an imbalance of the Treg to Th17 ratio in psoriasis.30,31 It was reported that the percentage of CD4+CD25+Foxp3+ (Tregs) was increased and that the percentage of CD4+IL-17+ (Th17) cells was decreased in rheumatoid arthritis after MSC treatment.32 Junji Xu et al. reported that MSC infusion directed T cells toward Treg and Th2 cells while suppressing Th17 responses and alleviating Sjogren syndrome (SS) symptoms.13 Collectively, these studies suggest that MSCs play an important role in regulating immune homeostasis.