Flare-up reaction on murine contact hypersensitivity. I. Description of an experimental model: rechallenge system.

In this experiment, a 'rechallenge system' was established in BALB/c mice to study a local immunological reaction of contact hypersensitivity (CH). Briefly, mice were sensitized by a single painting with 25 microliters of 0.5% dinitrofluorobenzene (DNFB) on the shaved back skin on Day 0. On Day 5, they were challenged with 20 microliters of 0.2% DNFB on each left ear, and on Day 33 challenged again with either painting 20 microliters of 0.2% DNFB on their both ears or intravenous administration of 15 mg of dinitrobenzene sulphonic acid (DNBS). As the result, marked ear swelling was observed by the second challenge only on the first challenged site and these responses were clarified to be antigen specific. In in vitro experiments, it was shown that only the cells from the regional lymph node of the skin, which were previously elicited on challenge, were enhanced to proliferate by DNBS, which was added into the culture medium. These results suggest that there is a local immunological mechanism to respond to the specific antigen only on the site in which CH reaction has been elicited previously. The results from this 'rechallenge system' may help to explain some pathological mechanisms of such chronic diseases as fixed drug eruption or chronic contact dermatitis, which recur easily in skin lesions involved previously.