Effects of Pityrosporum ovale on proliferation, immunoglobulin (IgA, G, M) synthesis and cytokine (IL-2, IL-10, IFN gamma) production of peripheral blood mononuclear cells from patients with seborrhoeic dermatitis.

The aetiology of seborrhoeic dermatitis (SD) is still unknown. An increased number of Pityrosposurm ovale in lesional skin of patients with SD has been suggested to play a crucial role in the pathogenesis of the disease since double-blind trials with antifungal drugs (e.g. ketoconazole) have shown that these agents result in a significantly reduced disease intensity. The frequent association of HIV infection and SD may be due to a suppressed cell-mediated immunity. In order to characterize the role of the humoral and cellular immune response in patients with SD the effects of a P. ovale extract on the proliferation of, and interleukin-2 (IL-2), IL-10 by an interferon-gamma (IFN gamma) production, and immunoglobulin (IgA, IgG, IgM) synthesis by peripheral blood mononuclear cells (PBMC) from patients with SD were studied in vitro. Healthy volunteers served as controls. PBMC from normal donors responded with a significantly increased proliferation to P. ovale antigen, whereas cells from patients with SD did not. Additionally, IL-2 and IFN gamma production by PBMC from patients with SD was markedly depressed compared with normal cells after stimulation with P. ovale. However, stimulation of PBMC from SD patients with P. ovale antigen induced significantly increased IL-10 synthesis. IgA, IgG and IgM synthesis was significantly increased in cultures of PBMC from patients with SD whether the cells were antigen-stimulated or not. Our results support the assumption that strong skin colonization with P. ovale in SD is due to an altered cellular immunity, which may be induced by increased IL-10 secretion.