Immune sensitization to yeast antigens in ASCA-positive patients with Crohn's disease

Alimentary antigens may play a role in the perpetuation of inflammation in Crohn's disease (CD). Yeast antigens are widespread components of food. A proportion of CD patients develop antibodies against the yeast Saccharomyces cerevisiae (ASCA), but little is known about the cellular immune reactivity against food antigens in antibody-positive and -negative patients.

Lymphocytes from patients with CD, ulcerative colitis, and healthy controls were tested for their proliferative response after stimulation with the yeast antigen mannan and ovalbumin. The cellular phenotypes and activation markers were analyzed via FACS. Cytokine concentrations and antibody titers were determined by ELISA.

Only lymphocytes of ASCA-positive patients with CD proliferated after stimulation with mannan. These lymphocytes expressed increased activation markers (CD25, CD69). Activation of T cells was mediated by antigen-presenting cells and was associated with increased tumor necrosis factor-alpha (TNF-alpha) levels. The immune reactivity to ovalbumin was predominantly found in CD patients. It was weaker compared with mannan, independent of ASCA status, and also present in healthy controls.

A disturbed humoral and cellular response to the yeast antigen mannan is specifically seen in a subgroup of CD patients. This phenomenon may be due to a loss of tolerance toward yeast and is possibly genetically determined.