Participation of T lymphocytes in cutaneous allergic reactions to drugs.

Immunological mechanisms implicated in drug allergic reactions are not yet well understood, but there is 'in vivo' and 'in vitro' evidence that T lymphocytes are involved in these hypersensitivity reactions. The cutaneous lymphocyte-associated antigen (CLA) is the skin homing receptor and is involved in targeting a skin-selective memory T lymphocyte to cutaneous sites of chronic inflammation. We have seen that CLA expression is increased in circulating T lymphocytes of patients who develop a drug allergic cutaneous reaction, these cells are activated and their CLA values tend to become normal in parallel with the disappearance of skin symptoms, demonstrating that CD3+ CLA+ cells are involved in the immunological mechanisms responsible for the pathogenesis of the chronic inflammation process in cutaneous drug reactions.