a, Activity of β-hexosaminidase released to the extracellular media of BMCMCs stimulated with medium alone (control) or indicated stimuli including different concentrations of culture supernatant of S. aureus 8325-4. b, Activity of β-hexosaminidase in supernatants of MC/9 cells stimulated with 10% of culture supernatant from LAC S. aureus wild type (LAC WT) or isogenic mutants deficient in PSM-α peptides (LAC Δpsmα), PSM-β peptides (LAC Δpsmβ), δ-toxin (LAC Δhld), LAC wild type expressing vector alone (LAC pTX_Δ16), LAC deficient in δ-toxin expressing vector alone (LACΔhld pTX_Δ16) and strain complemented with δ-toxin plasmid (LACΔhld pTX_Δhld). Control represents 10% tryptic soy broth (TSB) medium. c, Histamine concentrations in culture supernatant of FSMCs after stimulation with indicated stimuli including synthetic δ-toxin at 30 μg ml⁻¹ for 15 min. Data represent means ± s.d. of triplicate cultures. Results are representative of at least three independent experiments (a–c). P value refers to comparisons between experimental and control groups (a–c). d, Electromicroscopic images of FSMCs stimulated with synthetic δ-toxin (30 μg ml⁻¹) for 15 min. Images of unstimulated (Control) and ionomycin-treated FSMCs are also shown. Representative of at least 20 images. e, Expression of δ-toxin in Staphylococcus culture supernatants (0.5 μl per well). Loading of lanes with synthetic δ-toxin (10 ng, 100 ng) is shown as reference. Representative of three experiments. f, C57BL6 (WT) and MC-deficient (Kit^w-sh/w-sh) mice were injected intradermally into the left and right ears with δ-toxin (100 μg) or PBS, respectively. One representative mouse for each group is shown. Representative of eight mice per group. g, Quantification of Evans blue extracted from skin tissue of WT, Kit^w-sh/w-sh and Kit^w-sh/w-sh reconstituted with BMCMCs is shown. Dots represent individual ear samples from two independent experiments. NS, not significant; *P < 0.05; **P < 0.01; ***P < 0.001, two-tailed t-test.