IL21 and flatulence: Additionally in a rat study Wen et al have reported that the expression of IL-17, IL-21, IL-6, and IL-23 were significantly increased in mitral valve tissues in rats with RHD compared with normal group and the serum IL-17 and IL-6 concentrations were significantly higher in RHD rats.13 They thought that the expression of Th17 cell-associated cytokines is not induced by acute infection of GAS.