Identification of the G213-reactive protein as S100A9. (A) Tissue lysates derived from the lungs of untreated (left lane) and BCG-challenged (right lane) guinea pigs were resolved on SDS-PAGE, and western blotting was conducted with G213 (upper panel) and Ab to β-actin (lower panel). The 15-kDa species specifically recognized by G213 is indicated with an asterisk. The 30-kDa bands observed on both lanes may represent nonspecific signals. (B) Tissue lysates derived from the bone marrow, spleen, lymph nodes, and thymus of an untreated guinea pig were prepared, and western blotting was performed as in panel A. The 15-kDa species specifically recognized by G213 is indicated with an asterisk. (C) Bone marrow cells obtained from an untreated guinea pig were lysed, and immunoprecipitation (IP) was performed with either control IgG (left lane) or G213 (right lane). Samples were resolved on an SDS-PAGE gel, followed by immunoblotting with G213. The 15-kDa species specifically recognized by G213 is indicated with an asterisk. (D) Cell lysates derived from HEK293T cell transfectants expressing either FLAG-tagged S100A9 or HA-tagged S100A8 as well as mock-treated cells were resolved on SDS-PAGE gels, and immunoblotting with Abs to FLAG, HA, and β-actin as well as G213 mAb was conducted.