Role of Malassezia colonization in cutaneous immune response

Abstract

Malassezia yeasts are part of the cutaneous microflora and are also associated with a number of skin diseases such as pityriasis versicolor, seborrheic dermatitis, and atopic dermatitis (AD). Among organisms of the Malassezia species, M. globosa and M. restricta are highly associated with AD. However, their precise role in AD has remained uncertain. We first attempted to identify major allergens from M. globosa using a proteomics analysis. Immunoblotting showed that IgE-reactive components with molecular masses of 40-45 kDa proteins were detected by 100% (28 of 28) of sera from AD patients. The IgE-reactive allergens corresponding to the 42 kDa protein (MGp42) were identified by two-dimensional immunoblotting, and partially sequenced by MALDI-TOF MS with post source decay (PSD) of the peptide digest. Comparison of sequences with known protein sequences revealed that MGp42 showed similarity to the heat shock protein (hsp) family. Our studies have also demonstrated that human keratinocytes responded to the two Malassezia species with different Th2-type cytokine profiles, i.e. M. globosa induced IL-5, IL-10, and IL-13 secretion from the keratinocytes, whereas M. restricta induced IL4 secretion. These findings suggest that M. globosa and M. restricta play a synergistic role in triggering or exacerbating AD by stimulating the Th2 immune response.