Reactivity and persistence of local immunological memory on murine contact hypersensitivity

In a rechallenge system examining murine contact hypersensitivity to DNFB in BALB/c mice, the reactivity to the specific antigen at the previously responded site and the persistence of an immunological memory were investigated. Flare-up reactions were induced 4 weeks after the first challenge only at the previously responded site by local or systemic administrations of minute quantities of a specific antigen. The intensity of ear swelling was dependent on the quantity of applied antigen at the time of the rechallenge. The local hypersensitivity to the specific antigen observed in the previously responded site and the regional lymph node persisted for at least 1 year. These results suggest that the sensitivity to a specific antigen at the previously responded site is intensified and the immunological memory persists for a long time. This may explain the mechanisms by which chronic contact dermatitis recurs readily at the limited site by exposure to minute quantities of causative antigens.