Identity of the paramagnetic element found in increased concentrations in plasma of cancer patients and its relationship to other pathological processes.

Electron spin resonance (ESR) analysis plus chemical determinations show that the predominant ESR signals seen in frozen solutions of human plasma are due to the copper protein ceruloplasmin. The elevation of ceruloplasmin con centration above normal values in pathological processes is positively correlated with the increased ESR signal height seen in patients with cancer, infections, and myocardial infarctions. The relationship of the increased ESR signal to an immunological response was studied in rabbits and was found to be indirect and probably related to nonspecific stress. The identification of the predominant paramagnetic species in plasma as ceruloplasmin provides additional insight into evaluation of reports of increased free radicals in plasma.