FIG 3 .

Detection of headless HA proteins on the surfaces of transfected cells. Full-length and headless HA constructs were expressed in 293T cells by plasmid transfection. At 24 h posttransfection, cells were trypsinized and HA proteins on the cell surface were stained using polyclonal antiserum 3951 (for PR8) or MAb 12D1 (for HK68) before analysis by flow cytometry. (A) Mock-transfected cells stained with immune serum 3951 (gray) are compared to cells transfected with pDZ PR8 HA (red) or cells transfected with pCAGGS PR8 2G, 4G, or PG headless HA constructs (blue). (B) Mock-transfected cells stained with MAb 12D1 (gray) are compared to cells transfected with pCAGGS HK68 HA (orange) or cells transfected with pCAGGS HK68 2G, 4G, or PG headless HA constructs (green).