Innate and adaptive immune responses towards commensals have been suggested to play a role in triggering chronic inflammation in IBD, which is associated with a breakdown of immune tolerance. A number of IBD patients suffer from food intolerances showing an improvement of K-7174 dihydrochloride well-being by avoiding special nutritive components. However, the relevance of the relation between an exaggerated immune response against food antigens and the occurrence of food intolerance in IBD patients remains an open question. In the present study we analysed in parallel serum and fecal Abs specific for dietary and microbial antigens in a cohort of IBD patients and controls. The objective of this study was to investigate whether increased local or systemic levels of anti-microbial Abs in IBD patients correlate with levels of anti-food Abs, which would argue for a general loss of immune tolerance towards luminal Lupeol antigens. However, our results reveal that on the systemic level only Abs directed against some microbial antigens are elevated in CD but not UC patients, whereas anti-food Abs showed no general alterations in IBD patients. Anti-food IgA levels were slightly elevated in CD patients with a stricturing/penetrating phenotype. These patients have also elevated anti-microbial Abs levels, a finding that confirms the results of several former studies. Altogether, these findings argue for a more general loss of tolerance to intestinal antigens in severely affected CD patients that very likely have a stronger disturbance of the intestinal barrier than CD patients without stricturing and penetrating lesions. Those patients generally have a milder disease course and/or shorter disease duration and only show enhanced Ab levels towards selected microbial antigens. Surprisingly, anti-food IgG levels were decreased in CD and UC patients with arthropathy, an extraintestinal manifestation of IBD which occurs in about 30% of patients. The reason for these findings remains completely elusive and requires further investigation.