Fig. 1.

Depiction of process of immunoprecipitation of cell surface protein and either subsequent visualization of immunoprecipitation products after SDS-PAGE and Western blotting or preparation and analysis of products by mass spectrometry. The first step of the CMAII strategy is to demonstrate by indirect immunofluorescence the presence of plasma antibodies binding to the outside of a cell line; this is measured quantitatively by an analytical flow cytometer. The second step (depicted) is to immunoprecipitate and visualize any cell surface antigen(s) from the cell line (surface-labeled by biotin) using individual plasmas selected from the first step. The third step (depicted) is the preparation and mass spectrometry analysis of patient and control immunoprecipitates to identify the cell surface antigen(s) and to assess other proteins present in the immunoprecipitates.