The humoral and cellular immune-status was studied in 30 patients with seborrhoeic dermatititis. Increased frequencies of natural killer cells were found in 46% of patients. Furthermore, subnormal mitogen stimulation responses were demonstrated in 13 patients, whereas two individuals were found to have very high numbers of activated T lymphocytes in peripheral blood. Higher-than-normal total serum IgG and IgA was observed in 14 and 11 patients, respectively. For nine of 12 patients with skin lesions, dermal perivascular cell infiltrates were seen. The majority of the infiltrating cells reacted with anti-CD4 antibodies. HLA-DR-expressing keratinocytes were found in two biopsies. The study suggests that patients with seborrhoeic dermatitis may have depressed T-cell function. This could have a bearing on their susceptibility to the Pityrosporum ovale-associated dermatitis. The very high frequencies of activated T cells observed in the peripheral blood of two otherwise healthy seborrhoeic individuals suggests that intermittent systemic immune activation may occur. Seborrhoeic dermatitis is a common skin disease.1 It can be diagnosed by its characteristic red to yellow-brown lesions covered with greasy scales distributed in areas with a high number of sebaceous glands, such as the scalp, face and upper trunk.1 There is an association between seborrhoeic dermatitis and the lipophilic yeast Pityrosporum ovale but its exact aetiological role is not known.2 The yeast is a member of the normal cutaneous flora3 but also the aetiological agent of pityriasis versicolor4 and Pityrosporum folliculitis.5 P. ovale can activate complement via the direct and alternative pathways.6,7 This may play some part in the induction of inflammation. Serum antibodies against P. ovale have been found in normal individuals.8-11 In seborrhoeic dermatitis, both normal11,12 and high13 serum antibody levels have been demonstrated. A cell-mediated immune reponse to P.ovale has been found in normal human adults using P. ovale extracts in lymphocyte-transformation studies.14 In the present investigation, the humoral and cellular immune status of patients with seborrhoeic dermatitis was analysed. Blood samples and skin biopsies, from lesions and normal skin, were studied.
