Figure 1.

Interferon-γ (IFN-γ) and not interleukin-4 (IL-4), tumour necrosis factor-α (TNF-α) or granulocyte–macrophage colony-stimulating factor (GM-CSF) primes human mast cells (huMCs) for enhanced production of reactive oxygen species (ROS) and bacterial killing of Staphylococcus aureus. Human MCs were pre-treated with IFN-γ (20 ng/ml), IL-4 (20 ng/ml), TNF-α (20 ng/ml) or GM-CSF (20 ng/ml) for 48 hr before the addition of S. aureus (20 bacteria : one huMC). Extracellular ROS production was determined by Diogenes chemiluminescence for 1 hr at 30-second intervals at 37° (a) and bacterial killing determined after 3 hr incubation by counting CFUs of cell lysates on agar plates after a 24-hr culture at 37° (b). Results are shown as either kinetic data of single experiments of cells in the absence (thin lines) or presence (bold lines) of bacteria (a) or means ± SE (b) performed in triplicate and n = 3 independent experiments for one huMC donor. Differences between individual groups was tested for statistical significance by Kruskal–Wallis one-way analysis of variance on ranks with Bonferroni correction for multiple comparisons (***P ≤ 0·001 for comparison with control cells not treated with cytokines).