By Everard L. Napier, M.R.C.S., L.R.C.P. (Lond.). In charge Kala-azar research, Calcutta School of Tropical Medicine. Second edition. 185 pages of text with 15 charts in the text, 18 plates, and an appendix of references to literature, author index and subject index. Oxford University Press. London, Bombay, Calcutta, Madras, 1927
Eosinophil peroxidase (EPO) is a major component of the large cytoplasmic granules of eosinophils, and is released onto the surface of schistosomula when eosinophils adhere to antibody and complement coated organisms. EPO is a strongly cationic protein, which can bind to the surface of schistosomula with retention of peroxidatic activity. The binding per se was not toxic to the organisms under our conditions, but EPO-coated schistosomula were rapidly killed when H2O2 and halide were added, under conditions in which uncoated schistosomula were unaffected. The toxicity of the surface-bound EPO system was not significantly inhibited by albumin (20 mg/ml), in contrast to the complete inhibition by this concentration of protein when the EPO was free in solution. Purified polymorphonuclear leukocytes (PMNs) from normal donors were toxic to uncoated schistosomula in medium containing antischistosomal antibody and complement, and this toxicity was significantly increased when EPO was bound to the surface of the organisms. The toxicity of PMNs to EPO-coated schistosomula was inhibited but not abolished by the hemeprotein inhibitor azide. This is compatible with the involvement of surface-bound EPO in an enzymatic attack on the organism, utilizing H2O2 generated by PMNs stimulated by adherence to antibody and complement-coated schistosomula. PMN adherence to schistosomula is increased by surface-bound EPO, and this also may contribute to the enhancement of neutrophil-mediated toxicity by EPO. These findings indicate a mechanism by which two inflammatory cells, the eosinophil and neutrophil, may interact to enhance the destruction of a target organism.