[Yeast-like fungi malassezia (pityrosporum): clinical and immunological aspects fo study].

The normal flora is typified by the yeast-like fungi Malassezia (Pityrosporum). Successful attempts at treating patients with atopic and seborreic dermatitis, pityriasis versicolor, and psoriasis with antifungicides confirm the involvement of these fungi in the etiology and development of these diseases. In patients with various skin diseases, an immune response to M. furfur is specific. In those with psoriasis, it is characterized by the higher chemoatractant activity of polymorphonuclear leukocytes stimulated by a M. furfur extract and by the immune response of IgG antibodies with immunoreactive proteins having a molecular weight of 100-120 kD. Patients with atopic dermatitis show a hyperimmune IgE-mediated response to M. furfur, with its specific Th2-lymphocytes inducing the atopic cytokines (IL-4, IL-10) that stimulate allergic reactions to other allergens. Those with pityriasis versicolor had impaired keratinocytic pigment exchange due to azelainic acid produced by M. furfur. The cause of transformation of the yeast phase of M. furfur to the mycelial one is presumably to be changes in the composition of fatty acids of the sebaceous glands due to increased androgen concentrations.