IgE-sensitization to cellular and culture filtrates of fungal extracts in patients with atopic dermatitis

Background: Patients with atopic dermatitis may experience exacerbations of eczema triggered by various inflammatory stimuli. One mechanism may be IgE-mediated reactions to dermatophytes since these patients are more likely to acquire skin infections with dermatophytes and may become sensitized. Objective: This study investigates IgE-sensitization to fungi in patients with atopic dermatitis and compares the biologic activity of culture filtrates and cellular fungal extracts. The following allergen extracts were provided as culture filtrates and cellular extracts: Candida albicans, Fusarium moniliforme, and Penicillium notatun. In addition, Pityrosporum ovale and Trichophyton rubrum cultures were included in the test panel. Methods: Fifteen patients with clinical findings suggesting dermatophytosis and 11 controls were selected. Each subject was tested by leukocyte histamine release and skin prick test to each fungal extract. The extracts were separated and reduced by sodium dodecylsulfate polyacrylamide gel electrophoresis and analyzed by IgE-immunoblotting with sera from all study subjects. Results: Fourteen patients (93%) reacted to one or several fungal extracts by releasing histamine when challenged in vitro. By immunoblotting experiments, patient sera showed binding to a wide range of components in all extracts. Patient sera recognized allergenic components shared by culture filtrates and cellular extracts but with higher frequent and greater intensity in culture filtrates. Although culture filtrates generated more frequent and potent IgE-reactions than the cellular extracts, the difference was not statistically significant. Biologic potency was similar when evaluated by skin prick tests and leukocyte histamine release. Conclusion: Patients with atopic dermatitis may develop specific IgE-antibodies to a number of fungi as demonstrated by IgE-immunoblotting. In selected patients, fungi may trigger an IgE-mediated reaction that may contribute to the exacerbation of eczema. Approximately, one-half of the patients, however, produced IgE-antibodies to fungal (glyco)proteins without a significant histamine release or skin test response possibly because of nonspecific interaction with carbohydrate moieties on IgE and poor biologic activity of IgE antibodies directed to cross-reactive carbohydrate determinants of fungal glycoproteins. This warrants caution when interpreting clinical relevance of serologic measurements of fungal IgE-antibodies.