Cytokine responses and cell death induced by hornfels and porphyr particles of different sizes: Comparison to quartz. A) TNF-α responses, B) MIP-2 responses, C) Cell viability and D) Apoptosis. The macrophages were exposed to ≤ 2.0 μm and ≤ 10 μm particles of porphyr, hornfels and quartz for 8 h (TNF-α) or 20 h (MIP-2, viability and apoptosis). The cytokine release was analysed by ELISA, cell viability by the ability to exclude PI as assessed by fluoroscense microscopy and apoptosis by flow cytometry after Hoechst 33258 staining. The data are related to the surface area of the particles. The results represent the mean +/- SEM of three independent experiments.