Cell-mediated immune responses to Malassezia furfur serovars A, B and C in patients with pityriasis versicolor, seborrheic dermatitis and controls.

It has been postulated that patients with Malassezia furfur-associated dermatoses have a deficient cell-mediated immune response to M. furfur. This study examined the cell-mediated immune responses to M. furfur serovars A, B and C of 10 patients with pityriasis versicolor and 10 age- and sex-matched controls; and 10 patients with seborrheic dermatitis and 10 age- and sex-matched controls. The responses to each serovar of M. furfur were assessed using the lymphocyte transformation assay and the leukocyte migration inhibition assay. The lymphocyte transformation responses of the patients with pityriasis versicolor to M. furfur serovars A, B and C (0/10, 6/10 and 5/10 respectively) were not significantly different from those of controls (0/10, 2/10 and 1/10). However, for patients with seborrheic dermatitis, significantly more patients' lymphocytes responded to serovars B and C (6/10 and 6/10 respectively) than those of controls (1/10 and 1/10). No patient or control responded to serovar A. In the leukocyte migration inhibition assay, the leukocytes from a greater proportion of patients with pityriasis versicolor (5/7) responded to serovar B than controls (2/10); and the leukocytes from a greater proportion of patients with seborrheic dermatitis (4/10) responded to serovar C than controls (0/9). Thus, this data did not indicate the presence of any cell-mediated immune deficiency to M. furfur in patients with pityriasis versicolor or seborrheic dermatitis, as measured by the lymphocyte transformation assay or the leukocyte migration inhibition assay. The greater responsiveness of T lymphocytes from patients may indicate that T lymphocytes might be involved in the pathogenesis of these diseases.