IL21 and major depressive disorder: Interestingly, we show here that the expression level of Il1β was downregulated in CSDS depression mice compared with controls, as were cytokines specific for Th17 cells, Il17A, Il21, and Il22. Consistently, elevated levels of IL17 are associated with symptomatic reduction in depressed patients treated with a bupropion-selective serotonin reuptake inhibitor combination (58).