The effects of high-level band 3 coexpression are the same in K562/D and K562/cE cells.

The effects of coexpressing B3 and B3EQ in K562/Rh cells were indistinguishable, suggesting that the band 3–mediated enhancement of Rh antigen reactivity is due to the presence of the band 3 molecule itself rather than its activity. High-level coexpression was defined as the level of band 3 expression at which FL1 is approximately equal to 200 with BRIC 71. The histograms shown here illustrate the data listed in Table 4 for K562/D+B3EQ clone 1 (left column; using K562/D+pBn clone 2 as control) and in Table 5 for K562/cE+B3EQ clone 1 (right column; using K562/cE+pBn clone 2 as control). The effects of high-level band 3 coexpression were the same for K562/D and K562/cE cells. In all clones coexpressing high levels of B3 or B3EQ, the affinity of the cells was increased significantly for antibodies directed against Rh polypeptides (BRIC 69, 3- to 4-fold) and against RhAG (LA18.18, 3- to 5-fold).