The cytokine observed most often in atopic dermatitis (AD) is IL-4, but a role for IL-5 and IFN-γ in the late and delayed phase reactions has been suggested. In AD with head, neck and shoulder distribution, hypersensitivity to saprophytic yeasts is an important pathogenetic factor. The yeast allergens include both the mannan polysaccharides and the proteins. Mannans are major cross-reacting allergens likely to be involved in the pathogenesis of AD.
To characterize the humoral, lymphoproliferative and cytokine (IL-2, 4, 5 and IFN-γ) responses of peripheral blood mononuclear cells (PBMCs) induced by Candida albicans mannan and protein antigens in AD.
Fifteen AD patients and seven healthy controls were included. Ficoll-isolated PBMCs were stimulated by PHA and laboratory-generated mannan and protein extracts of C. albicans. Lymphocyte proliferation was measured and cytokine production was studied by ELISA. The antigen-specific IgG and IgE antibodies were analysed by ELISA and nitrocellulose RAST.
In AD mannan (P < 0.005) and protein (P < 0.002), specific IgE levels were higher than in healthy controls. Both mannan and protein-specific lymphoproliferations (both: P < 0.02) were higher in AD than in healthy controls. Mannan, but not protein, induced long lasting IL-2 and IL-4 productions from 24 h lasting up to 66–96 h and IL-5 and IFN-γ productions with elevated levels at 66 and 96 h. The mannan-induced IL-2 (P = 0.015) and IFN-γ (P < 0.005) were increased in AD as compared with healthy controls. Significant correlations were seen between the protein-induced proliferation responses and both serum total IgE (r = 0.59, P < 0.01) and protein-specific IgE (r = 0.65, P < 0.005). The mannan-induced IL-2 responses correlated with the specific IgE (r = 0.62, P < 0.01) and proliferation (r = 0.51, P < 0.02) and S-IgE level (r = 0.71, P < 0.002). Mannan-induced IL-4 and IFN-γ productions also correlated (r = 0.43, P < 0.05).
C. albicans mannan induced elevated IL-2 and IFN-γ responses in AD patients. The correlations of the cytokine responses with mannan-induced IgE and proliferation responses suggest that C. albicans mannan induced TH1 type cytokine responses are involved in AD.