CD44 is associated with Lck and Fyn kinases in the low-density membrane domains. After kinase assay on CD44 immunoprecipitates from pooled low-density fractions as in Fig 5B, left panel top, the immune complexes were washed in 0.5% Brij-58 lysis buffer, dissociated by SDS, and reimmunoprecipitated using the indicated antibodies. The immunoprecipitated proteins were separated by SDS-PAGE and visualized by autoradiography after 4 days of exposure. The total phosphoprotein profile associated with the primary CD44 immunoprecipitate is shown in the first lane.