[Principal cellular and molecular mechanisms of xenobiotic-induced hypersensitivity reactions]

Sensitization to xenobiotic first involves an interaction between the compound and antigen presenting cells such as Langerhans cells within the epidermis. This leads to the transdermal migration of this presenting cells towards draining lymph nodes. A second step consists in activation, proliferation and differenciation of CD4+ T cells, and CD8+ T lymphocytes involved in delayed hypersensitivity reactions such as contact dermatitis. T helper lymphocytes can differenciate into Th1 (producing interferon-gamma and interleukin (IL)-2) or Th2 (producing IL-4, IL-5, IL-10, IL-13) lymphocytes. Some experimental models allowed to demonstrate a link between Th1- or Th2-type responses and different hypersensitivity reactions. Specific antibody production also plays a key role in xenobiotic-induced allergy, especially IgE production involved in mastocytes degranulation and immediate hypersensitivity reactions.