There are still many questions to fully understand the relationships among gut bacteria, gut inflammation, and immune cells in the gut (Sefik et al., 2015), but current emphasis is focusing on: (1) Will TCR specificities against gut commensals on the CD4 T cell be important factors to developing gut inflammation under disease conditions such as IL-10 KO and transfer colitis model? The gene discussed is CD4; the disease is colitis.