Adjuvant effect of grifolan on antibody production in mice

The effects of grifolan (GRN), a gel-forming (1-->6)-branched (1-->3)-beta-D-glucan, on antibody production were examined. Sera from mice that were injected with GRN and trinitrophenyl ovalbumin (TNP-OVA) intraperitoneally showed a significantly increased level of anti-TNP IgG. However, injection of TNP-OVA alone showed a lower antibody level. Two hundred fifty microg of GRN and 10 microg of TNP-OVA gave the maximum production of anti-TNP antibody. Enhanced antibody production was also observed in the culture supernatant of splenocyte obtained from GRN-administered mice. The culture supernatant contained a significant amount of nitric oxide (NO) in the case of GRN-administered mice. To observe the effect of NO on the antibody production induced by GRN, N-monomethyl arginine (NMMA), an inhibitor of NO synthetase, was added to the splenocyte cultures. The antibody level of supernatants containing NMMA was higher than that of control supernatants. These results suggest that GRN can enhance antibody production and that NO induced by stimulation with GRN concomitantly with antibody production is a negative factor on the adjuvant activity. Inhibition of NO may increase the adjuvant effect of GRN.