Association molecules of CD9 in MS-5 cells. MS-5 stromal cells were surface-labeled with biotin and lysed with the indicated detergents (Triton-X100, digitonin, CHAPS). The cell lysates were immunoprecipitated with KMC8.8. The blot was reacted with avidin-biotin-immunoperoxydase complex, and the proteins were visualized using an ECL chemiluminescence system.