Objective: Lymphocytes are deeply involved in the initiation and perpetuation of inflammatory response in inflammatory bowel disease (IBD) and lymphocyte-derived proteins are associated with the pathogenesis of the disease. The aim of this study was to identify the altered protein profiles of lymphocytes from rats with colitis. Methods: Colitis models were induced by colonic administration of trinitrobenzene sulfonic acid (TNBS) in 50% ethanol in male SD rats. Seven days after administration of TNBS/ethanol, lymphocytes were harvested from mesenteric lymph nodes (MLNs) and proteins were extracted. Two-dimensional polyacrylamide gel electrophoresis and PDQuest 2D-image-analysis software were used to display and analyze the protein spots. The differentially-expressed proteins were identified by tryptic in-gel digestion and mass spectrometry. Real-time RT-PCR was used for selected transcripts to validate the findings of the proteomics analysis. Results: A total of 1,100 protein spots including 26 proteins with at least a two-fold difference in abundance between colitis and control groups were identified. Among all the detected spots, 17 were up-regulated and 9 were down-regulated. It was found that the altered proteins included the regulators of the cell cycle and cell proliferation, signal transduction factors, inflammatory factors, apoptosis-related proteins and metabolic enzymes. Conclusions: In lymphocytes of rats with TNBS-induced colitis, 26 altered proteins were identified. They involve inflammation, apoptosis, metabolism, and regulation of the cell cycle, cell proliferation, and signal transduction. © 2007 Birkhäuser Verlag.