Delayed-type hypersensitivity reactions to nominal protein antigens and to environmental allergens: similarities and differences.

Tuberculin-induced delayed type hypersensitivity and allergen-induced late phase responses are two types of cutaneous inflammatory reactions mediated by antigen-specific T cells and involving distinct pathophysiological mechanisms. In humans, different types of cellular infiltration as well as cytokine profiles have been ascribed to each reaction. A more precise analysis of these reactions shows that in fact they are complementary, intricated, and cross regulatory, and that they represent interesting models to evaluate the regulation of some pathological disorders.