[Immunologic principles of allergic contact eczema].

Epicutaneous sensitization against contact allergens is mediated by T lymphocytes. For activation of these T lymphocytes antigen has to be presented in association with Ia by Langerhans cells. A further signal for activation of this cell is provided by interleukin 2. The production of interleukin 2 is induced by interleukin 1, which can be also produced by keratinocytes (epidermal T-cell activating factor, ETAF). The activated T-effector lymphocyte is controlled by T-suppressor lymphocyte subpopulations. The interaction between these cells is genetically controlled. A defect in this genetic control may play a role in contact sensitization against various allergens.