Metabolism of H‐2 and Thy‐1 (Θ) alloantigens in murine thymocytes

The metabolism of Thy‐1 and H‐2 alloantigens was studied in murine thymocytes radiolabeled with ³H precursors or surface radioidinated. It was found that ¹²⁵I‐labeled Thy‐1 is rapidly shed from cultured thymocytes, whereas H‐2 alloantigens are not. [³H]galactose‐labeled Thy‐1 is also released from cultured thymocytes, whereas [³H]leucine‐labeled H‐2 alloantigens are not. These results support the concept that H‐2 alloantigens are integral macromolecules of the plasma membrane and suggest further that Thy‐1 is a peripheral one. Possible mechanisms underlying shedding are discussed.