Detection and molecular characterization of the thymus-brain antigen in human brain.

Anti-human brain sera were found to contain antibodies reacting with determinants present on murine thymocyte plasma membranes. This determinant is borne by the thymocyte-brain antigen of mouse thymocytes. The non species-specific determinant of the thymocyte-brain system is detectable on the thymocyte-brain antigen of human and mouse brain in comparable amounts. In contrast to these findings, the allogenic Thy-1 and the species-specific determinant of this system were only found on the thymocyte-brain antigen of mouse brain but not on the corresponding antigen of human brain. The molecular weight, Stokes radius and diffusion coefficient of the thymocyte-brain antigen of human and mouse brain are in good accordance with the data estimated for the corresponding antigen of murine thymocytes.