Peripheral CD4(+) T cell maturation recognized by increased expression of Thy-1/CD90 bearing the 6C10 carbohydrate epitope

The SPV16C10 IgM autoantibody recognizes a surface determinant, 6C10, that is highly expressed on all immature thymocytes, In contrast, its expression on peripheral T cells appears developmentally regulated, i.e., absent from most naive T cells in spleen of neonatal mice, but expressed on 40-80% of naive CD4(+) T cells in adult. In this paper, we demonstrate that SM6C10 re cognizes a carbohydrate epitope on the Thy-1 glycoprotein using immunopreci pitation analysis, by binding to affinity-purified Thy-1 in an ELISA, and b y sensitivity to N-glycosidase-F treatment. Retroviral Thy-1 gene transduct ion experiments into Thy-1(-) variant T cell lines and a pro-B cell line pr ovide evidence that 6C10 glycosylated Thy-1 expression is not restricted to T cells but depends on the recipient cell. Therefore, differences in 6C10 levels among Thy-1(+) T cells in mice likely reflect developmental regulati on of posttranslational modification of the Thy-1 glycoprotein, The ability of naive CD4(+) T cells to respond to anti-Thy-1 stimulation increases fro m neonate to adult, and 6C10(-) naive cells from adult mice respond poorly compared with 6C10(+) cells, similar to the cells in neonatal mice. These r esults suggest that there is functional maturation by peripheral CD4(+) T c ells that coincides with 6C10 glycosylated Thy-1 up-regulation, and natural autoantibody recognizes this 6C10 carbohydrate epitope.