Peroxidase-mediated iodination by guinea pig peritoneal exudate eosinophils

Leukocyte iodination, which requires the granular enzyme peroxidase, hydrogen peroxide generated by the cell, and an appropriate oxidizable cofactor such as iodide, was studied in guinea pig peritoneal exudates. Eosinophils had an active resting iodination which was increased approximately 10-fold by the addition of serum and zymosan. In contrast, neutrophils had barely detectable resting iodination, but marked stimulation also occurred employing serum and zymosan or preopsonized zymosan. Under all conditions tested eosinophil iodination was significantly greater than neutrophil iodination (P< 0.001). The role of the peroxidase system in iodination was confirmed by inhibition in the presence of 10^-3 M azide, cyanide, or aminotriazole. Inhibition by exogenous catalase and facilitation by superoxide dismutase substantiated the role of hydrogen peroxide. Autoradiographic and cell separation studies confirmed that the majority of iodination was cell or particle associated.