hGIIA coprecipitates a 57-kDa protein, vimentin, from the Hypo LB–insoluble/Hyper LB–soluble fraction of apoptotic T cells. (A) Apoptotic human T cells were incubated with or without hGIIA and lysed as described in “Materials and methods.” hGIIA was immunoprecipitated from the Hypo LB–insoluble/Hyper LB–soluble fraction. The immune complexes were separated by SDS-PAGE and revealed using Sypro Ruby. Pure hGIIA not incubated with T cells was also immunoprecipitated using the same procedures. (B) The 57-kDa band was collected, digested, and analyzed by MALDI-TOF-MS. The amino acid sequences of the 16 peptides identified by MALDI-TOF-MS are shown in bold. (C) Cells treated or not with an anti-Fas antibody were incubated with hGIIA as described in “Materials and methods.” Cells were sequentially lysed, and vimentin was immunoprecipitated from the soluble fractions with the antibody V4630. Proteins were separated by SDS-PAGE and transferred to PVDF membranes. The membranes were probed with the hGIIA antibody as described in “Materials and methods.”