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 IFNγ in colonie mucosa of patients affected by ulcerative c olitis and correlated it with clinical and biochemical parameters to identify th e context of this up regulation. We enrolled 21 patients affected by ulcerative colitis and 6 healthy subjects. We evaluated for each patient gender, age, durat ion of disease, clinical, endoscopic and histologic disease activity index, medi cal therapy, ESR, serum CRP, WBC, and serum α 1- acid glycoprotein. CD80, CD86 , and IFNγ expression in the colonie mucosa was quantified using reverse trans cription polymerase chain reaction. Statistical analysiswas performed using Mann - Whitney U test and Spearman’ s rank correlation test. Significance was set a t P<0.05. CD80 was detectable in seven patients, while CD86 and IFNγ expressio n was evident in all UC patients. CD80 and CD86 were not detectable in control s pecimens. Colonie CD80 expression was correlated to the age of the patients. CD8 6 expression showed an inverse correlation with duration of disease and a direct correlation with serum CRP levels and histologic grade of disease activity. IFN γ was not correlated with any of the examined parameter. Our study confirms a major role in ulcerative colitis pathogenesis for CD86 which correlates with his tologic grade of disease and with serum CRP levels, and its up- regulation seem s to be higher at the beginning of the disease. In “ in vivo“ conditions IFNγ may not be the only factor responsible for CD86 up- regulation in the ulcerati ve colitis colonic mucosa. 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 IFNγ in colon mucosa of patients affected by ulcerative colitis and correlated it with clinical and biochemical parameters to identify We enrolled 21 patients affected by ulcerative colitis and 6 healthy subjects. We evaluated for each patient gender, age, durat ion of disease, clinical, endoscopic and histologic disease activity index, medi cal therapy, ESR, serum CRP, WBC, and serum α 1-acid glycoprotein. CD80, CD86, and IFNγ expression in the colon mucosa was quantified using reverse transcript 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 IFNγ expressio n was evident in all UC patients. CD80 an CD8 6 expression showed an inverse correlation with duration of disease and a direct correlation with serum CRP levels and histologic grade of disease activity. was not correlated with any of the examined parameter. Our study confirms a major role in ulcerative colitis pathogenesis for CD86 which correlates with his tologic grade of disease and with serum CRP levels, and its up- regulation seem to be higher at the beginning of the disease. In ”in vivo " conditions IFNγ may not be the only factor responsible for CD86 up- regulation in the ulcerati ve colitis colonic mucosa.