Secretory antibodies reduce systemic antibody responses against the gastrointestinal commensal flora

Abstract

The humoral response to the gastrointestinal (GI) flora was analyzed in secretory Ig (sIg)-deficient polymeric IgR (pIgR)-/- mice and otherwise congenic C57BL/6 mice. While both strains carried an ileal flora of similar size and composition, increased bacterial translocation to mesenteric lymph node was demonstrated in pIgR-/- mice. Serum IgA was greatly increased in pIgR-/- mice compared with C57BL/6 mice and reacted with commensal organisms and food. Serum IgG levels in pIgR-/- mice were increased to 6-fold above that of C57BL/6 mice and included specificities that bound to selected flora antigens. The enhanced recognition of flora antigens in pIgR-/- mice was explored using ovalbumin (OVA..