Compensatory roles of CD8+ T cells in immune regulation in the gut with non-functional CD4+ Tregs

CD4⁺ regulatory T cells are known as master regulators that maintain the immune suppressive environment in the intestine. CD4⁺ Tregs need to migrate from the mucosal periphery into the draining lymph node via CCR7 to exert their suppressive effects. Here we investigated whether CCR7 deficiency resulted in failure of immune suppression in dextran sulfate sodium-induced colitis. Intestinal inflammation was not exacerbated in the absence of CCR7. Expression of IL-10, a representative suppressive cytokine, was enhanced in CCR7KO CD8⁺ T cells. Colon CCR7KO CD8⁺ T cells reduced the activation of CD4⁺ T cells. Plasmacytoid dendritic cells were also slightly increased during intestinal inflammation in the absence of CCR7. These results suggest that CD8⁺ T cells and dendritic cells have compensatory roles in immune regulation in the gut with non-functional CD4⁺ Tregs.