SUPPRESSION OF IgE ANTIBODY RESPONSE IN MICE BY A POLYSACCHARIDE, AZ9, PRODUCED BY KLEBSIELLA OXYTOCA STRAIN TNM3

ABSTRACT

A soil bacterium, Klebsiella oxytoca TNM3 was found to produce a polysaccharide named AZ9 that shows suppressive effects on IgE antibody response in mice. When mice were administered with 50∼ 100 mg/kg AZ9 subcutaneousely for 4 consecutive days after immunization with trinitrophenyl (TNP)-keyhole limpet hemocyanin, anti-TNP IgE production was significantly suppressed, while the level of anti-TNP IgM was affected marginally. In AZ9-administered mice, IL-4 secretion from splenic cells was reduced to ∼30% of the untreated control. Thus, AZ9 suppression of IgE production may be due to attenuating effects on the Th2-type response. Although oral administration of AZ9 alone had no effects on IgE production, ovalbumin (OVA)-induced oral tolerance of anti-TNP IgE response to TNP-OVA was markedly augmented when a suboptimal dose of OVA was administered orally in combination with AZ9. Collectively, our data suggest that AZ9 has beneficial suppressive effects on IgE-dependent allergic responses.