Contact hypersensitivity

Contact hypersensitivity is a simple in vivo assay of cell-mediated immune function in which exposure of epidermal cells to exogenous haptens results in a delayed-type hypersensitive reaction that can be measured and quantified. The Langerhans cell is the critical antigen-presenting cell in this reaction which initiates sensitization to haptens by presenting antigens to CD4-bearing T lymphocytes which, in turn, secrete lymphokines and recruit other cells to the site of the reaction. In the protocol described here, mice are shaved and the skin of their abdomens is exposed to a hapten. After 6 days (the afferent phase), the baseline ear thickness is measured prior to initiation of the efferent phase. Finally, the ear is treated epicutaneously with the hapten solution and ear thickness is measured in approximately 24 hr. The change in ear thickness after allergen treatment can be used to calculate the percent suppression of contact hypersensitivity.