TNF^+/+ mast cells reconstitute DTHRs in TNF^−/− ears but not in TNFR1^−/− ears. (A) Representative visualization of PMN infiltrates, tissue necrosis, and edema. Ear sections from TNF^−/− (top left), TNFR1^−/− (top right), mast cell-reconstituted TNF^−/− mice (bottom left), and TNFR1^−/− mice (bottom right) were fixed 24 hours after ear challenge and then stained with hematoxylin and eosin. (B) Hapten-specific DTHRs in C57BL/6 wild-type, TNF^−/−, TNFR1^−/−, mast cell–reconstituted TNF^−/−, or mast cell–reconstituted TNFR1^−/− mice. Ear swelling was measured 24 hours after TNCB challenge (n = 4-6). (C) Confocal microscopy of intracutaneously engrafted Cy5 (left) and red fluorescent protein (right) stained mast cells in ears of TNFR1^−/− mice 5 days after mast cell engraftment (top represents overview; bottom represents detail).