Genetic Dissection of the Cellular Pathways and Signaling Mechanisms in Modeled Tumor Necrosis Factor–induced Crohn's-like Inflammatory Bowel Disease

Recent clinical evidence demonstrated the importance of tumor necrosis factor (TNF) in the development of Crohn's disease. A mouse model for this pathology has previously been established by engineering defects in the translational control of TNF mRNA (Tnf^ΔAREmouse). Here, we show that development of intestinal pathology in this model depends on Th1-like cytokines such as interleukin 12 and interferon γ and requires the function of CD8⁺ T lymphocytes. Tissue-specific activation of the mutant TNF allele by Cre/loxP-mediated recombination indicated that either myeloid- or T cell–derived TNF can exhibit full pathogenic capacity. Moreover, reciprocal bone marrow transplantation experiments using TNF receptor–deficient mice revealed that TNF signals are equally pathogenic when directed independently to either bone marrow–derived or tissue stroma cell targets. Interestingly, TNF-mediated intestinal pathology was exacerbated in the absence of MAPKAP kinase 2, yet strongly attenuated in a Cot/Tpl2 or JNK2 kinase–deficient genetic background. Our data establish the existence of redundant cellular pathways operating downstream of TNF in inflammatory bowel disease, and demonstrate the therapeutic potential of selective kinase blockade in TNF-mediated intestinal pathology.