Luminal antigliadin antibodies in small intestinal bacterial overgrowth

Elevated antigliadin antibody levels in small intestinal luminal secretions of subjects with normal or only mildly abnormal small intestinal histology are considered indicative of "latent" or "potential" celiac disease. The purpose of this study was to determine whether small intestinal bacterial overgrowth (SIBO) might provide an alternative explanation for positive luminal antigliadin antibodies in such subjects.

Twenty-six adult subjects without predisposition to disturbed mucosal immunity were investigated with culture of small intestinal luminal secretions. Luminal total IgA and IgA-antigliadin antibody concentrations were measured by radial immunodiffusion and indirect enzyme immunoassay, respectively. Local mucosal counts of IgA-plasma cells were determined by immunohistochemistry. Small intestinal histology and intraepithelial lymphocyte counts were assessed by light microscopy. Corresponding serum antigliadin antibody concentrations were determined.

SIBO was present in 17/26 (65.4%) subjects. No subject with SIBO had villous atrophy. Luminal total IgA concentrations (p < 0.0005), mucosal IgA-plasma cell counts (p < 0.01), and intraepithelial lymphocyte counts (p < 0.01) were significantly increased in subjects with SIBO. Luminal IgA-antigliadin antibodies were detected in 6/17 (35.3%) subjects with SIBO and 0/9 (0%) subjects without SIBO. Luminal IgA-antigliadin antibody concentrations correlated significantly with luminal total IgA levels (p < 0.01) but not with serum values (p < 0.1). Serum IgG-antigliadin antibody concentrations were elevated in 2/6 (33.3%) subjects with SIBO and positive luminal antigliadin antibodies.

SIBO may be an alternative explanation to "latent" or "potential" celiac disease for positive luminal antigliadin antibodies in subjects with either normal or only mildly abnormal small intestinal histology, even when serum antigliadin antibody concentrations are elevated. Positive luminal antigliadin antibodies in SIBO probably occur as epiphenomena in the context of a graded mucosal immune response to local bacterial antigens.