OPTIMIZATION OF THE MOUSE EAR SWELLING TEST FOR IN-VIVO AND IN-VITRO STUDIES OF WEAK CONTACT SENSITIZERS

Murine models for the assessment of the contact sensitizing properties of chemicals rely on mouse ear swelling tests (Mest), which are not s ensitive enough to detect weak sensitizers. The aim of the present stu dy was to develop in mice an adjuvant-free Mest appropriate for in viv o detection of any type of sensitizer (weak to strong), and useful for in vitro assessment of contact sensitivity (CS). 3 haptens were teste d: dinitrochlorobenzene (DNCB), para-phenylenediamine (pPD) and isoeug enol. We compared various protocols for induction of the CS reaction, differing by the site of induction, the number of applications and the concentrations of the 3 haptens. Comparison of the induction site for optimal CS reaction showed that, in Balb/c mice, the back was a bette r site of induction than the abdomen. Detection of the sensitizing pro perties of weak sensitizers (pPD, isoeugenol) was possible using an ad juvant-free protocol, provided that the induction phase comprised hapt en applications on 3 consecutive days on the backs of animals. For DNC B, one application was sufficient to obtain optimal CS reaction. For a ll 3 haptens, a secondary response in vitro was obtained using semi-pu rified lymph node T cells from animals sensitized 5 days before with t he optimized Mest. These results demonstrate that the Mest could be a useful experimental model for the study of all types of contact sensit izers.