Modulatory effects of glucocorticoids on immunoregulatory functions of epidermal cells.

Accessory cell function of mouse and human epidermal cells (ECs) was analyzed by measuring their capacity to support the proliferative response of lectin-stimulated nonadherent thymic T cells (NATs). NATs exhibit low responsiveness to lectins, while the addition of ECs induced in a dose-dependent way either supportive or suppressive effects. Accessory function of ECs was not genetically restricted and could be partially replaced by soluble products of ECs. In vitro X-irradiation with 3000 R increased rather than impaired helper effects of ECs. In vitro exposure of ECs to hydrocortisone inhibits the production of stimulatory EC-derived factors and favor the production of factor(s) which suppress NAT proliferation. Additionally, ECs obtained from mouse skin to which glucocorticoids were topically applied, produced factor(s) which inhibited lectin-induced proliferation of NATs. Thus, it appears that immunosuppressive effects of topically applied glucocorticoids may partially be due to the abolition of the production of the factor(s) which stimulate cell proliferation within skin and/or to the enhancement of the activity of suppressive factor(s).