By using a cytotoxicity inhibition assay employing AKR anti-C3H thymocyte antiserum, we have determined the degree of expression of the thy-1 antigen in fractions of adult mouse brain. As expressed as cytotoxicity inhibitory capacity per mg protein with C3H whole brain arbitrarily assigned a value of 1.0, the following values were found: C3H cerebral cortex, 5.8; C3H cerebral cortex synaptosomes, 2.5: C3H whole brain myelin, 0.65; C3H cerebral cortex neurons, 0.16; and C3H cerebral cortex mitochondria, 0.10. Neither C1300 neuroblastoma cells nor any AKR neural fraction had detectable levels of thy-1.

The findings indicate that the thy-1 antigen is found mainly in mouse cerebral cortex and in synaptosomal fractions, whereas myelin fractions contain lower but perhaps significant amounts of thy-1. Cerebral cortex neurons, isolated by a method requiring a 90-min mild trypsinization at 37°C, did not display significant amounts of the thy-1 antigen.

These results lend themselves to further study in the area of differentiation and development of central nervous system components and in the area of central nervous system immunopathology.


This work was supported by Grant MS-889-B2 from the National Multiple Sclerosis Society and Grant NS-05572-13 from the National Institutes of Health.

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