Immune responses to environmental antigens that act on the skin: the role of lymphokines in contact dermatitis.

Immune responses to enviornmental agents affecting the skin may take various clinical forms, among which contact dermatitis is the most prominent representative of delayed-type hypersensitivity. Whereas in industrialized countries a relatively restricted amount of chemical agents is responsible for the majority of contact dermatitis cases, other factors from the environment such as natural flora, seasonal or nutritional factors may also play a role. Like other immune responses, contact dermatitis is strongly influenced by genetic factors and the existence of immune response genes, in part linked to the major histocompatibility complex, has been established in experimental animals. Whereas the formation of conjugates between skin-specific proteins and contactant allergens is held by some to represent an important feature in contact dermatitis, recent experiments suggest that the direct binding of contactants to monocyte and lymphocyte membranes represents the most efficient way in inducing sensitization of the T lymphocytes primarily responsible for contact hypersensitivity. At the effector level, complete inhibition of contact dermatitis and other delayed type hypersensitivity reactions by an antiserum prepared against guinea pig lymphokines (especially migration inhibition factor) offers strong evidence that lymphokines, as products of activated lymphocytes, also play a decisive role in vivo. The properties of antibodies raised against purified lymphokine fractions are reviewed. Localized contact dermatitis reactions, as well as accompanying phenomenons such as flar-up reactions and generalized maculopapular rashes, may, however, still involve other elements than T lymphocytes and lymphokines. The participation of other secondary cell types and of local antibody formation is briefly discussed.