Protein profiles of peripheral blood mononuclear cells are useful for differential diagnosis of ulcerative colitis and Crohn's disease.

Background: Effective biomarkers for discrimination between ulcerative colitis (UC) and Crohn's disease (CD) have not been established yet. In this study, we analyzed protein profiles of peripheral blood mononuclear cells (PBMCs) of the patients to find such a biomarker.

Methods: Peripheral blood mononuclear cell proteins from 17 UC patients, 13 CD patients, and 17 healthy controls were separated by two-dimensional gel electrophoresis. The intensities of individual protein spots were subjected to discriminant analysis of UC and CD using the SIMCA-P+program.

Results: We found that 547 protein spots were commonly detected among the UC, CD, and healthy groups. Orthogonal partial least squares-discriminant analysis using 276 protein spots clearly discriminated the UC patients from the CD patients (R (2) 0.994; Q (2) 0.462). A similar analysis using a further selected 58 protein spots showed higher performance for discrimination of the diseases (R (2) 0.948; Q (2) 0.566). Eleven out of the 58 protein spots were successfully identified; these were functionally related to inflammation, oxidation/reduction, the cytoskeleton, endocytotic trafficking, and transcription. In addition, the PBMC protein profiles were useful for the prediction of disease activity in the UC and the CD patients, and they were also useful for predicting disease severity and responses to treatments in the UC patients.

Conclusions: PBMC protein profiles are useful for the discrimination of UC from CD. The profiles could be a potent biomarker for the differential diagnosis of these diseases. Further investigation of the proteins which contributed to the discrimination could promote elucidation of the pathophysiology of UC and CD.