The intriguing role of anti-commensal bacteria antibodies in sera of colitic rats

Abstract

BACKGROUND A variety of commensal bacterial taxa elicit serum IgA responses resulting in protection against polymicrobial sepsis, whereas anti-commensal IgG may have deleterious role in gastrointestinal and systemic inflammation. OBJECTIVES The aim was to determine the systemic levels of specific antibodies directed to autologous E.coli in rats of Albino Oxford (AO) and Dark Agouti (DA) rat strains during colitis. METHODS Rats were intrarectally injected with ethanol or trinitrobenzenesulfonic acid (TNBS, 10 or 40mg/kg) whereas controls received saline in the same manner. Sera were tested for the level of anti-E.coli antibodies of IgG1, IgG2a, IgG2b and IgA classes by ELISA. RESULTS Both rat strains developed colitis, but the degree of colon necrosis and hyperemia were slightly greater in DA than in AO rats and the survival rate was significantly lower in DA relative to AO rats. Among saline-treated controls, the levels of IgG1, IgG2a, and IgG2b anti-E.coli antibodies were comparable between rat strains, whereas the amounts of IgA were significantly higher in DA compared to AO rats. Development of colitis significantly increased the amount of anti-E.coli antibodies of IgA and IgG2a classes in sera of AO rats, and those of IgG2a and IgG2b classes in sera of DA rats. Hence, mostly beneficial role of IgA and probably deleterious role of IgG2b antibodies directed to commensal E.coli during colitis may be suggested, whereas the role of anti-E.coli antibodies of IgG2a classes remains intriguing.