Defining the antigen determinant for T-cell-mediated contact dermatitis using p-phenylenediamine: a gateway to chemical immunology.

By binding to host proteins to form haptens, low-molecular-weight compounds such as p-phenylenediamine (PPD) can become contact sensitizers. In this issue, Jenkinson et al. demonstrate that it is possible to use chemically characterized hapten-protein complexes to analyze T-cell responses in cells from allergic individuals. This approach may help in the development of in vitro tests for diagnosing contact dermatitis.