MIP-2 response and apoptosis induced by various concentrations of stone particles. The macrophages were exposed to mylonite, gabbro, feldspar, basalt and quartz (≤ 10 μm) for 20 h. A, B) show MIP-2 responses and C, D) Apoptosis. In A and C the MIP-2 responses and apoptosis, respectively, were related to the mass of the particles, and in B and D to the surface areas of the particles. The MIP-2 release was analysed by ELISA, and apoptosis by flow cytometry after Hoechst 33258 staining. The results represent the mean +/- SEM of three independent experiments.