The fungal cell wall component beta-1,3-glucan has an adjuvant effect on the allergic response to ovalbumin in mice

The polyglucose beta-1,3-D-glucan is a major structural component of the ce ll wall of yeasts and fungi. In the present study, the adjuvant activity of beta-1,3- glucan from the fungus Sclerotinia sclerotiorum (SSG) on the res ponse to the model allergen ovalbumin (OA) was studied, using the popliteal lymph node assay (PLNA) in BALB/c mice. The adjuvant activity on the local cellular response was determined by measuring the weight, cell number, and proliferation of the extracted PLNs. The levels of OA-specific immunoglobu lin (Ig) E, IgG1, and IgG2a in serum were measured by enzyme-linked immunos orbent assay (ELISA). Groups of 8 mice were given either SSG + OA, SSG alon e, or OA alone on d 0. Thereafter they were exsanguinated on d 20, or reinj ected with OA on d 21, before exsanguination on d 26 or 33. Only on d 26 wa s SSG + OA found to significantly increase the PLN weight and cell numbers, but not cell proliferation (thymidine incorporation), compared with OA or SSG alone. SSG + OA was also found to significantly increase both the anti- OA IgE and IgG1 levels on d 20, 26, and 33 compared to OA alone. Compared t o SSG alone, SSG + OA increased the OA-specific IgE and IgG1 levels signifi cantly on d 26 and 33, but not on d 20. A similar increase was not found fo r IgG2a. Our results show that beta-1,3-D-glucan provides a clear Th2-depen dent (allergic) immune response to OA, indicated by elevated levels of IgE and IgG1 and not IgG2a, in the mouse model used.