Analysis in deoxycholate of three antigenic specificities associated with the rat Thy-1 molecule.

Three antigens similar in tissue distribution can be identified on rat thymocytes; the Thy-1.1 antigen, a rat specific xenoantigen, and a rat-mouse cross-reacting xenoantigen. To determine if these three antigens were on the same molecule their behavior in detergent-solubilized extracts from thymocytes was studied. Membrane fragments containing Thy-1.1 activity were prepared by a rapid method involving the use of Tween-40 detergent, and were solubilized in deoxycholate. The 150 000 x g supernatant from this extract contained approximately 50% of the original Thy-1.1 and xenoantigen activity. The supernatant was chromatographed on Sephadex G-200, and subjected to zone sedimentation on sucrose gradients in H2O and 2H2O to determine the hydrodynamic properties of the antigens. The three antigens migrated in identical fashion in all cases, and behaved as a molecule of 28 000 daltons molecular weight. When the antigenically active fraction, recovered after chromatography on Sephadex G-200, was passed through an immunoabsorbent consisting of rabbit antibody to one of the xenoantigens, all three antigens were equally depleted compared with passage through a control column. The results of these experiments suggested that Thy-1.1 antigen and the two xenoantigens were closely associated and most probably all on the Thy-1 molecule.