Purification and characterization of mouse brain Thy-1.2 differentiation alloantigen.

Subcellular fractionation of C57BI/6J mouse brains produced a crude synaptosome preparation which contained virtually all of the Thy-1.2 antigenic activity of the isotonic whole brain homogenate. The Thy-1.2 was solubilized from the synaptosomes, following delipidation with acetone, by deoxycholate extraction. A glycoprotein fraction rich in Thy-1.2 was isolated from the bulk of the detergent-soluble material by lectin affinity chromatography. Fractionation of the lectin retentate by gel filtration chromatography produced a single peak of Thy-1.2 activity purified more than 2000-fold over the original homogenate. SDS polyacrylamide gel electrophoresis of this material revealed a single band which corresponded to an apparent molecular weight of 24,000. Amino acid composition data indicated that the protein portion of the molecule is similar to Thy-1.1 from mouse lymphoblastoid cells. Carbohydrate analysis revealed a qualitative similarity between mouse brain Thy-1.2 and Thy-1.1 from rat brain. Structural differences which could account for the Thy-1.1 and Thy-1.2 antigenic distinctions are apparently too subtle to be detected by compositional analysis.