CBL-b and c-CBL associated preferentially with p85β. (A) Jurkat T cells were transfected with empty vector, or with vectors encoding rHAp85α and β. At 36 hours after transfection, cells were collected and activated with CD3+CD28 for different times. Total extracts were immunoprecipitated with CBL-b or c-CBL antibodies, and p85 binding was analyzed in WB using anti-HA antibody. Total p85 was used as equal protein concentration control. Histograms show relative signal plus or minus SD (n = 3) of rHAp85α or rHAp85β binding to CBL-b and c-CBL. (B) Extracts from the assay shown in Figure 2D were immunoprecipitated using anti–c-CBL or anti–CBL-b Ab, resolved by SDS-PAGE, and examined by WB using anti-HA Ab. The graphs are as in Figure 2D. Scheme showing the potential interaction domains of p85β to CD28 and CBL after activation. *P < .05.