Syndecan-1 ectodomain is shed from the surface of myeloma cell lines. (A) Presence of shed syndecan-1 ectodomain in the media conditioned by myeloma cell lines. Syndecan-1 was detected using an immuno-dot blot analysis with anti–syndecan-1 antibody (B-B4). (B) Western blot of partially purified syndecan-1 from media conditioned by ark cells probed with B-B4, showing the presence of intact syndecan-1 ectodomain and ectodomain after digestion with heparitinase.