Transfection of wild-type and mutant CD11/CD18 dimers into COS-7 cells. Wild-type CD18 cDNA or the mutants G284S, G284R, Y131S, and Y131F were transfected into COS-7 cells together with the wild-type cDNA for CD11a, CD11b, or CD11c. CD11/CD18 expression was monitored by flow cytometry using the monoclonal antibody 1B4. The background histograms (broken lines) were obtained using an irrelevant isotype-matched antibody. Expression profiles of CD11/CD18 transfectants are shown as solid lines. The subtracted profiles (using Cellquest software) are shown in solid black. The percentage of gated positive cells (%GP), mean fluorescence intensity (MFI), and expression index (EI), derived from %GP × MFI are also shown.