AIM:To investigate whether oral tolerance is inducible during the active phase of dextran sulfate sodium(DSS)-induced colitis.METHODS:Colitis was induced in 6-to 8-wk-old female BALB/c mice by the administration of 2%DSS.To induce oral tolerance,mice that received water with DSS[DSS(+)]and mice that received autoclaved water[DSS(-)]were intragastrically(i.g.)administered ovalbumin(OVA)as a tolerogen before systemic challenge with OVA.Following this,serum levels of OVA-specific Ig E antibodies were measured.In mice with activecolitis,CD4+CD25+Foxp3+cell and B10 cell frequencies were evaluated using flow cytometry.Cytokine m RNA expression profiles were evaluated by reverse transcription real-time polymerase chain reaction.RESULTS:Regardless of the presence of DSS colitis,OVA-specific immunoglobulin E concentrations were significantly reduced in mice that were i.g.administered OVA compared to mice that were i.g.administered PBS[DSS(+):4.4(4.2-9.5)ng/m L vs 83.9(66.1-123.2)ng/m L,P<0.01;DSS(-):27.7(0.1-54.5)ng/m L vs116.5(80.6-213.6)ng/m L,P<0.01].These results demonstrated that oral tolerance was induced in both the presence and absence of colitis.In the spleen and mesenteric lymph nodes(MLN),the frequencies of CD4+CD25+Foxp3+cells and B10 cells,both of which are associated with oral tolerance,did not significantly change.In the spleen,interferon-γm RNA expression significantly decreased in mice with colitis[DSS(+):0.42(0.31-0.53)vs DSS(-):1.00(0.84-1.39),P<0.01].The expression levels of other cytokines did not significantly change.CONCLUSION:Oral tolerance is inducible during active DSS colitis.The stability of regulatory cell populations in the spleen and MLN in colitis might correlate with these results. AIM: To investigate whether oral tolerance is inducible during the active phase of dextran sulfate sodium (DSS) -induced colitis. METHODS: Colitis was induced in 6-to 8-wk-old female BALB / c mice by the administration of 2% DSS .To induce oral tolerance, mice that received water with DSS [DSS (+)] and mice that received autoclaved water [DSS (-)] were intragastrically administered ovalbumin (OVA) as a tolerogen before systemic challenge with OVA.Following this, serum levels of OVA-specific Ig E antibodies were measured in mice with activecolitis, CD4 + CD25 + Foxp3 + cell and B10 cell frequencies were evaluated using flow cytometry. Cytokine m RNA expression profiles were evaluated by reverse transcription real-time polymerase chain reaction .RESULTS: Regardless of the presence of DSS colitis, OVA-specific immunoglobulin E concentrations were significantly reduced in mice that were igadministered OVA compared to mice that were igadministered PBS [DSS (+): 4.4 (4.2-9.5) ng / m L vs 83.9 (66.1-123.2) ng / m L, P <0.01; These results in that oral tolerance was induced in both the presence and absence of colitis. SS (-): 27.7 (0.1-54.5) ng / m L vs 116.5 (80.6-213.6) ng / m L, P < The frequencies of CD4 + CD25 + Foxp3 + cells and B10 cells, both of which are associated with oral tolerance, did not significantly change. In spleen, interferon-γm RNA expression was significantly decreased in mice with colitis [DSS (+): 0.42 (0.31-0.53) vs DSS (-): 1.00 (0.84-1.39), P <0.01]. The expression levels of other cytokines did not significantly change. inducible during active DSS colitis. The stability of regulatory cell populations in the spleen and MLN in colitis may correlate with these results.