Recent investigations pointed out that various disorders of immune function can be observed in patients with psoriasis vulgaris (PV). Accordingly, several data indicate disturbancies of the humoral immunity in this disease, which can be considered as an increase of B-lymphocyte activity [1,4,8,10]. In contrast, studies of cellular immune reactions have revealed a slight tendency to depressed sensitization to external antigens [5,13]. Furthermore, a significant decrease of T-lymphocyte proportion was published by several authors [3,6,7], and functional studies of T-lymphocytes showed some alterations as well, as the decreased lymphocyte response to Concanavalin A (Con A) [8] and the lower suppressor activity of T cells [9].
A principial component of natural cell-mediated cytotoxicity has been found to be a subpopulation of lymphocytes, so-called natural killer (NK) cells. It is well known that the majority of the human NK cells are T-lymphocytes bearing Fc receptors for IgG [14]. The biologic significance of these cells remains obscure, but there is evidence that NK cells may be involved in the resistance to malignancies [11]. Because of the above mentioned impairments of the T-lymphocyte response in PV it seemed to be of value to study the NK cell activity in this disease.
Patients
Twenty-nine untreated patients (aged 21 -55 years) having suffered from PV of plaque type between 1 and 17 years, were involved in the present investigations. None of these patients exhibited other diseases. Prior to this study, the patients had not received corticosteroids or immunosuppressive drugs during a period of 2 months. A group of 23 healthy adults (aged 18-49 years) was used as a control.
EfJ'ector Cells and Cryopreservation
Peripheral blood mononuclear cells were separated on Ficol-Hypaque gradients according to the method described by B6yum [2]. The cells were cryopreserved and thawed by the method of Strong et al.