Description:
<jats:p>An immediate reaction was investigated during repeated challenge testing for contact hypersensitivity to dinitrofluorobenzene ( DNFB) in BALB/c mice. The mice were sensitized to DNFB on back skin and repeatedly challenged with the same hapten on the left ear at 1 week intervals. The ear after the 5th challenge showed biphasic responses which consisted of an immediate and a delayed‐type reaction. The reactions were hapten specific. Mast cell‐deficient WBB6F1 W/W<jats:sup>V</jats:sup> mice did not show any immediate reaction, while congenic normal mice showed both immediate and delayed‐type reactions. Histologically, numerous dermal mast cells were found in the left ear of repeatedly challenged BALB/c and WBB6F1 normal mice, while there were few mast cells in the ear of WBB6F1 W/W<jats:sup>V</jats:sup> mice. Anti‐
DNP IgE antibodies were detected in BALB/c, WBB6F1 normal and W/W<jats:sup>V</jats:sup> mice after repeated challenge with DNFB. Intradermal injection of anti‐IgE antibodies in the repeatedly DNFB‐challenged ear elicited an immediate reaction. These results suggest that immediate contact hypersensitivity develops through the production of anti‐ DNP IgE antibodies and an increase in dermal mast cells after repeated challenge with DNFB.</jats:p>