Induction of cutaneous granuloma formation by PAG depends on release of TNFα by MCs.

(A) MCs in the direct vicinity of early PAG-induced CGs exhibit signs of profound degranulation. As assessed by quantitative histomorphometry, the extent of MC degranulation 1 hour after PAG injection in C57BL/6 mice was scored as “none” (< 10% of granules exhibited staining alterations and/or exteriorization), “moderate” (10%-50%), or “extensive” (> 50%), and expressed as means ± SEMs (data pooled from 5 mice). (B) Unpurified (purity about 1%) and purified (purity > 95%) peritoneal MCs of C57BL/6 mice release serotonin after incubation with PAG. Data were pooled from 3 independent experiments and expressed as means ± SEMs. (C) TNFα-deficient mice exhibit reduced recruitment of MΦ to sites of CG formation after injection of PAG compared with wild-type mice. Data were pooled from 5 or more mice per genotype and time point in 3 independent experiments. (D) Migration of MΦ to granulomas inKit^W/Kit^W-v mice 12 hours after induction is repaired only by reconstitution of the skin with connective tissue–type MCs obtained from TNFα+/+ mice, but not after reconstitution with MCs from TNFα-deficient mice. Data were pooled from 8 or more mice per genotype in 2 independent experiments. Data in all panels are shown as means ± SEMs. *P < .05, **P < .005, ***P < .001.