Figure 1.

CTLA4Ig binding to wild-type and mutant CD80 as revealed by flow cytometry. (a) CD80 expression. J558 cells were transfected with either vector alone (J558-Neo), wild-type CD80 (J558-B7), or CD80 mutants (W88>A, J558-B7W; Y201>1, J558-B7Y). J558 cells were stained with a saturating amount of biotinylated anti-CD80 mAb 10.16A, and the amount of mAb bound was determined by phycoerythorin-avidin. (b) Binding of J558-B7, J558-B7W, J558-B7Y, and J558-Neo to varying concentrations of CTLA4Ig. Data presented are mean fluorescence after normalization of cell surface CD80 expression as described in Materials and Methods. The experiments have been repeated three times with similar results.