NEUROTOXICITY OF HUMAN EOSINOPHILS

Eosinophils contain a substance that is neurotoxic when injected intracerebrally or intrathecally into laboratory animals - an effect known as the 'Gordon phenomenon'. We found neurotoxic activity in eosinophils from three patients with eosinophilic syndromes by injecting cell preparations into rabbits and guinea pigs. These animals developed a syndrome of muscular rigidity and ataxia, progressing to severe paralysis. No neurotoxic activity was found in preparations of polymorphonuclear or mononuclear leukocytes from normal donors. Examination of the brains of affected animals confirmed widespread loss of Purkinje cells, as described by earlier investigators. A new finding was severe spongy change occurring in the white matter of the cerebellum, brainstem and spinal cord. Electron microscopic examinations showed that vacuoles formed within the myelin sheaths of axons by separation of lamellae. Associated axonal degeneration was common and was also seen occasionally in peripheral nerves. Gray matter in the cerebral hemispheres and spinal cord was normal. This eosinophil-derived neurotoxin was partially purified by ultracentrifugation of sonicated eosinophils and fractionation of the supernate by gel filtration. Fractions with neurotoxic activity eluted at a position consistent with a molecular weight of approximately 15,000. The neurotoxic activity of this material withstood lyophilization and dialysis but was destroyed by heating to 90°C. Injection of eosinophil-derived neurotoxin into laboratory animals may provide a useful short-term experimental model for study of mechanisms of damage to myelinated nerve fibers. The clinical significance of the Gordon phenomenon has yet to be established.