P624. Food and microbial IgG and IgA levels in the serum and feces of patients with inflammatory bowel disease and controls
Patients with inflammatory bowel disease (IBD) and in particular Crohn's disease (CD) have elevated serum antibody (Ab) levels against several microbial antigens such as anti-Saccharomyces cerevisiae Abs (ASCA). It remains poorly defined whether food-specific IgG and IgA levels are also elevated in IBD patients.
Using ELISA we analysed specific IgG and IgA levels directed against 3 major food antigens (wheat extract; milk extract; purified ovalbumin) and 3 microfloral antigens (Eschericia coli lysate; Bacteroides fragilis lysate; ASCA) in the serum and feces of patients with CD (n = 52 for serum and n = 20 for feces), ulcerative colitis (UC; n = 29; n = 17), acute gastroenteritis/colitis (GI; n = 12; n = 9) and age-matched controls without inflammation in the gastrointestinal tract (n = 61; n = 39).
Food- and microbial-specific IgG and IgA are detectable in the serum of almost all patients and controls. CD but not UC patients have higher ASCA and anti-C. fragilis IgG and IgA levels, whereas antibody levels against E. coli and food antigens are not significantly different within the patient groups and controls. Subgroup analysis revealed that CD patients with severe diseases defined by stricturing and penetrating pattern have higher anti-food and anti-microbial IgA concentrations compared to CD patients with a non-stricturing/penetrating phenotype and controls. In contrast, CD and UC patients with arthropathia have lower anti-food IgG levels compared to patients without arthropathia and controls. Treatment with anti-TNF-alpha Ab in CD patients is associated with significantly decreased ASCA IgG and IgA as well as anti-E. coli IgG. No correlation of anti-food or anti-microbial Ab levels with disease activity, CRP, WBC and the presence of food intolerance was observed. In fecal homogenates specific IgG and IgA are not detectable in >50% and >25% of the samples, respectively. Specific IgG levels are generally higher in CD and GI patients compared to controls and UC patients. Specific stool IgA levels are highest in non-IBD individuals and lowest in UC patients.
Our results show that, in contrast to anti-microbial Ab, anti-food Ab levels in the serum are not generally altered in IBD patients. However, in certain patient subgroups serum anti-food Ab levels are either up- or downregulated. Changes in fecal anti-food and anti-microbial IgG and IgA abundance may reflect increased serum leakage into the gut and diversified local immune activation.