The animal model described in this unit is one of several that have been used to study the immunopathogenesis of inflammatory bowel disease. The model employs the use of 2,4,6-trinitrobenzenesulfonic acid (TNBS), which induces severe colonic inflammation when administered intrarectally in SJL/J mice. The colitis which results from this procedure presents clinical and histopathological findings that resemble those seen in Crohn's disease. The unit describes the critical parameters needed for successful induction of TNBS-colitis as well methods for monitoring and grading disease levels. A support protocol for isolating lamina propria mononuclear cells from mouse colons is also included.