Polyacrylamide gel analysis of IL-15/sIL-15Rα complex purified from an overproducing human cell line. (A) HPLC-purified human IL-15 and sIL-15Rα produced by a HEK293-derived cell line were mixed in a molar ratio 1:1, and IL-15/IL-15Rα complexes were visualized in Coomassie blue-stained denaturing SDS-polyacrylamide gel (top panel) and in Coomassie blue-stained nondenaturing polyacrylamide gel (bottom panel). (B-C) IL-15/IL-15Rα shown in panel A was detected by Western immunoblot. Complexes were analyzed under denaturing condition (top panels) or under nondenaturing condition (bottom panels) using a goat anti–human IL-15Rα antibody (B) or a goat anti–human IL-15 antibody (C).