Contact Hypersensitivity.

Contact hypersensitivity (CHS) is a simple in vivo assay of cell-mediated immune function in which exposure of epidermal and dermal cells to exogenous haptens results in a delayed-type hypersensitivity (DTH) reaction that can be measured and quantified. Epidermal Langerhans cells and dermal dendritic cells are the critical antigen-presenting cells in this reaction which initiate sensitization to haptens by presenting antigens to CD4- and CD8-bearing T lymphocytes which, in turn, secrete cytokines 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 5 or 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 ∼24 hr. The magnitude of the ear swelling reaction after allergen treatment reflects the strength of the immune response.