Cross-reacting IgE and IgG antibodies to Pityrosporum ovale mannan and other yeasts in atopic dermatitis

Atopic dermatitis (AD) patients often demonstrate positive skin prick test results and serum IgE antibodies to a range of different yeasts. This has b een thought to be due to crossreactivity. In this study, the cross-reactivi ty of IgE and IgG antibodies between mannan and crude antigens of Pityrospo rum ovale, Candida albicans, and Saccharomyces cerevisiae and crude antigen s of Cryptococcus albidus and Rhodotorula rubra was examined by RAST and EL ISA inhibition with two serum pools of AD patients. We found cross-reacting IgE and IgG antibodies. In the IgE response, the main cross-reacting patte rn was the mannan region, although inhibition could be achieved also with c rude antigens of C. albicans, S. cerevisiae, and, to some extent, C. albidu s. P. ovale was the most potent inhibitor of IgE-binding components, and ag ainst it the highest IgE antibody levels were detected in AD serum pools. I n contrast, C. albicans was found to be the most important inducer of IgG a ntibodies, since the IgG level against P. ovale mannan in both AD serum poo ls was very low. Cross-reacting antibodies were also seen in ELISA inhibiti on with both crude and mannan antigens, but since the IgG antibody level of P. ovale mannan in AD serum pools was low, further studies are needed to c onfirm the IgG results.