Figure 1.

Flow cytometric analysis of CD80 and CD86 expression in transfected COS cells. COS cells transfected with expression vector pCD80 or pCD86 (grey histograms) or with pCDNA3 (black histograms) were stained with fluorescein isothiocyanate (FITC)-conjugated specific monoclonal antibodies (mAbs) against CD80 or CD86 (upper panel). Binding to their counter receptor, cytotoxic T-lymphocyte antigen-4 (CTLA-4), was determined using fluorescence-activated cell sorter (FACS) analysis by incubating transfected COS cells with an appropriate dilution of FcCTLA-4 followed by incubation with a specific FITC-conjugated anti-mouse immunoglobulin G (IgG) (lower panel).