Peripheral cytokine profile in Chilean patients with Crohn's disease and ulcerative colitis

Crohn's disease (CD) and ulcerative colitis (UC) belong to the group of inflammatory bowel diseases (IBD), with complex ethiopathogenic factors that include an unbalanced immune and inflammatory response to commensal and food antigens. The differential diagnosis between CD and UC is performed using clinical, endoscopic, histopathological, serological and radiological methods; however between 10-15% of IBD patients are diagnosed as "unclassified colitis". Further research into IBD is necessary in order to develop additional diagnostic tools. The aim of this work was to see if the Th1, Th17 or Th2 immune pattern, represented by CD4+ lymphocytes producing IFN-gamma, IL-17 and IL-5 or IL-13, respectively (CD4/IFN-gamma+, CD4/IL-17+,CD4/IL-5+ or, CD4/IL13+), are useful peripheral markers which can be used to differentiate between UC and CD. Peripheral blood samples were taken from IBD patients from the Clinic Hospital of the University of Chile. The percentage of IFN-gamma-, IL-17-, IL-5- or IL-13-expressing CD4+ cells was determined by flow cytometry in phorbol ester- (PMA) and calcymycin-activated blood samples. The percentages of the CD4+ cell populations producing each cytokine were compared between UC and CD. IFN-gamma production by CD4+ lymphocytes was significantly higher in CD compared to UC and the control. The percentage of IL-17-expressing cells was significantly higher in CD patients compared to to the control; however, there were no differences between UC and CD; or between UC and healthy individuals. No significant differences were observed between the different groups as regards the representative Th2 cytokines. This study suggests that, under pathogenic conditions, several immune profiles may be operating, in the development of IBD. Although peripheral IFN-gamma and IL-17 expression, as indicators of the immune pattern, may help in the diagnosis of IBD, other cytokines and adaptive immune markers should be analyzed to allow better differentiation between the two entities.