Our findings are consistent with previous reports where mice housed under GF environment failed to develop intestinal inflammation in multiple experimental colitis models, including genetic deficiencies in IL-10 and IL-2, and the T cell transfer and chemically induced colitis models.21–23 The major reason for the reduced inflammation is likely due to the absence of microbiota driving activation of innate and adaptive immunity24–26 (Figure 6). Here, IL2 is linked to colitis.