The pathophysiological role of IgG antibody to fungi antigen widely distributed in environment such as Candida albicans in bronchial asthma has not been clarified. Wells of microtiter plate were coated with the extract of Candida albicans and then IgG antibody was immobilized on the wells by incubation with patient's serum. After cultivation of eosinophils on the well, degranulation of eosinophils, as assessed by quantitation of EPX in the supernatant, has been observed. Degranulation was completely abrogated after depletion of IgG in the serum and also decreased by incubation of the cells with anti-CD32 antibody, or anti-CD18 antibody, but not anti-CD23 antibody. Immune complex, which had been prepared by incubation of the extract of Candida albicans with patient's serum, also evoked degranulation of eosinophils. We have examined whether degranulation can be induced by two purified antigens of Candida albicans, i.e., mannan A and acid protease. IgG antibody to acid protease was detected at no or minimal levels in most sera and the antigen did not induce degranulation. On the other hand, mannan A induced degranulation. This observation may be due to response for the presence of IgG antibody to mannan A in the sera. These results suggest that immobilized IgG induced degranulation of eosinophils through Fc gamma RII (CD 32) on eosinophils and mannan A is a major allergen associated with IgG-induced eosinophil degranulation.