Expression and phosphorylation status of Lu/BCAM in GD and CTR RBCs. (A-B) Lu/BCAM cell-surface expression was measured in RBCs from 16 CTRs and 18 GD patients using anti-Lu/BCAM monoclonal antibody F241 and flow cytometry. Compared with control RBCs, a higher geometric fluorescence intensity was observed in mature RBCs (***P < .0001; Mann-Whitney test [A]) and reticulocytes of GD patients (**P < .01; Mann-Whitney test [B]). Horizontal lines represent medians. (C) Typical results of radiophospholabeling of GD and CTR RBCs followed by immunoprecipitation of Lu/BCAM protein by a specific anti-Lu antibody. The phosphorylated proteins were detected using phosphoimager and the corresponding total immunoprecipitated Lu/BCAM proteins were quantified by Western blot (WB) using a biotinylated anti-Lu/BCAM antibody. The P/WB ratio (arbitrary units) estimates the proportion of phosphorylated Lu/BCAM protein. (D) P/WB ratio obtained with CTR (n = 16) and GD (n = 18) RBCs. Horizontal lines represent medians. We observed more phosphorylated Lu/BCAM in GD RBCs than in CTR RBCs (*P = .0113; Mann-Whitney test).