IL-1R antagonism or deficiency abrogates CHS, whereas IL-1β pretreatment of P2X₇^−/− mice restores it. (A) Anakinra was injected i.p. on days 5, 3, and 1 before sensitization. Sensitization and challenge were performed as in Fig. 1. (B) Mice of the indicated strains were treated with 100 µl of 3% TNCB or acetone as vehicle control on day 0. On day 5, all mice received 20 µl of 1% TNCB on the dorsum of the ear pinna as challenge. (A and B) One representative of three independent experiments is shown. (C) WT and P2X₇^−/− mice were injected with IL-β in PBS/0.1% BSA or vehicle control 30 min before sensitization in the dorsum of the left ear. Mice were sensitized by topical application of 3% TNCB on the dorsum of the right ear on day 0. Challenge was performed on day 5 with 1% TNCB on the dorsum of the left ear. One experiment was performed. (A–C) Data represent the mean increase in ear thickness ± SD of groups of five mice (**, P < 0.005; ***, P < 0.001).