NOD2 and colitis: Thus, one possible explanation of the studies presented above (showing that over-expression of BS-NOD2 leads to loss of protection from TNBS-colitis) is that the ability of intact NOD2 to protect mice is negated by the fact that the BS-NOD2 transgenic mice express NOD2 that exhibits auto-activation or is hyper-responsive to MDP and thus manifest more persistent TNBS-colitis.