Objectives: Crohn's disease (CB) represents a chronic inflammatory condition of the gut which is caused by an inadequate immune response driven by external factors in a genetically susceptible host. The involvement of dipeptidyl-peptidase IV/CD26 (DPP IV/CD26) in the pathogenesis of CB is effected through proteolitic cleavage of various types of immunomodulatory supstrates and its costimulatory function, but the role of related proteins dipeptidyl-peptidases (DP) 8 and 9 is yet to be elucidated. The main objective of this research was to investigate whether experimental colitis causes any changes in gene and protein expression of these enzymes and their supstrates, peptide YY (PYY) and substance P (SP), whose involvement in CB is indicated. Material and Methods: TNBS-colitis was induced in CD26-defficient (CD26-/- ) and C57BL/6 mice sacrificed on days 2 (inflammation), 7 (healing) and 20 (recovery) following treatment. Clinical and changes in body mass were noted and the level of colon damage was assessed by patohistological and histomorphometric analysis. Transcriptional activity of colon DP8, DP9, DPP IV/CD26, PYY and SP was done by qPCR, while colon and serum protein expression was assessed by ELISA. DPP IV/CD26-like and DP8/9 colon and serum enzyme activity was determined spectrophotometrically using DP8/9 and DPPIV/CD26 specific inhibitors. Results: Clinical parameters, body mass loss, hepatosomatic index and significant colon shortening in mice sacrificed on day 2, along with characteristic changes in the crypts, lead to the conslusion that both mouse strains developed TNBS-colitis. mRNA expression of DPP IV/CD26, DP8 and DP9 did not differ significantly in inflammation in CD26-/- mice, while a decrease in DP9 on day 2 and DP8 on day 7 was noted in C57BL/6 mice (P < 0,05). Colon concentration of DP8 and DP9 is more affected by inflammation in C57BL/6 mice, but a significant increase(P < 0,05) in CD26-/- mice confirms the expected up-regulation of these 2 enzymes in conditions of CD26 defficiency. Contrary to expectations, intracellular DP8 and DP9 were found in abundance in serum and DP8/9 activity was decreased on day 2. Also, DPP IV/CD26 activity and expression follow the same pattern on both local and sistemic level, which is in level with previously published data. The pattern of mRNA PYY expression change differs between strains, while SP seems to be incerased in CD26-/- and C57BL/6 mice. Colon X concentration of PYY and SP is in line with gene expresssion alterations and it can be concluded that TNBS-colitis affects sistemic SP more than PYY. Conclusion: Induction of TNBS-colitis generated changes of gene and protein expression of DP8 and DP9 at local and systemic level. Thus, their involvement in inflammation development and/or healing process of intestinal mucosa is highly implicated, especially in terms of CD26- defficiency.