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 been thought to be due to cross‐reactivity. In this study, the cross‐reactivity of IgE and IgG antibodies between mannan and crude antigens of Pityrosporum ovale, Candida albicans, and Saccharomycescerevisiae and crude antigens of Cryptococcus albidus and Rhodotorula rubra was examined by RAST and ELISA inhibition with two serum pools of AD patients. We found cross‐reacting IgE and IgG antibodies. In the IgE response, the main cross‐reacting pattern was the mannan region, although inhibition could be achieved also with crude antigens of C. albicans, S. cerevisiae, and, to some extent, C. albidus. P. ovale was the most potent inhibitor of IgE‐binding components, and against it the highest IgE antibody levels were detected in AD serum pools. In contrast, C. albicans was found to be the most important inducer of IgG antibodies, since the IgG level against P. ovale mannan in both AD serum pools was very low. Cross‐reacting antibodies were also seen in ELISA inhibition 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 confirm the IgG results.