Several studies showed that costimulatory signals on antigen presenting cells are up-regulated in inflammatory bowel disease. We quantified the expression of CD80, CD86, and IFNgamma in colonic mucosa of patients affected by ulcerative colitis and correlated it with clinical and biochemical parameters to identify the context of this up regulation. We enrolled 21 patients affected by ulcerative colitis and 6 healthy subjects. We evaluated for each patient gender, age, duration of disease, clinical, endoscopic and histologic disease activity index, medical therapy, ESR, serum CRP, WBC, and serum al-acid glycoprotein. CD80, CD86, and IFNgamma expression in the colonic mucosa was quantified using reverse transcription polymerase chain reaction. Statistical analysis was performed using Mann-Whitney U test and Spearman's rank correlation test. Significance was set at P < 0.05. CD80 was detectable in seven patients, while CD86 and IFNgamma expression was evident in all UC patients. CD80 and CD86 were not detectable in control specimens. Colonic CD80 expression was correlated to the age of the patients. CD86 expression showed an inverse correlation with duration of disease and a direct correlation with serum CRP levels and histologic grade of disease activity. IFNgamma was not correlated with any of the examined parameter. Our study confirms a major role in ulcerative colitis pathogenesis for CD86 which correlates with histologic grade of disease and with serum CRP levels, and its upregulation seems to be higher at the beginning of the disease. In "in vivo" conditions IFNgamma may not be the only factor responsible for CD86 up-regulation in the ulcerative colitis colonic mucosa.