CD4 and infection: The susceptibility of the C3H mice to fatal infection is largely governed by a robust activation of R-spondin2 gene, upregulation of the Wnt pathway, and associated loss of epithelial differentiation and increased CD4+ T cell activation.67,68 Thus, C. rodentium T2SS can potentially contribute to some or all of these aspects of severe infection, and the specific effectors and their mechanism of action should be investigated in future studies.