Detection of eosinophil O^−⋅₂ production by the DMPO spin trapping technique. (A) EPR spectrum on isolated, unstimulated hepatic granuloma eosinophils (2 × 10⁶ cells/mL) suspended in HBSS in the presence of DTPA (0.1 mmol/L) and DMPO (100 mmol/L) after 25 minutes of culture at 37°C. (B) EPR spectrum 25 minutes after addition of zymosan (1 mg/mL). (C) The same as (B) except in the presence of opsonized zymosan (1 mg/mL). (D) The same as (C) except in the presence of superoxide dismutase (CuZnSOD; 30 U/mL). Results are representative of five separate experiments. The spectra seen in tracings (A) through (C) are those of DMPO/⋅OH (A^N = A^H = 15.0 G).