Specific binding of HTSU-IgG to activated primary CD4⁺ T cells shows saturable dose-dependent kinetics.

PHA-activated IL-2 dependent (♦) or unactivated (●) primary CD4⁺ cord blood T cells (10⁶) isolated from cord blood were incubated with the indicated amount of HTSU-IgG or, as a negative control, SUA-IgG (125 ng/mL). Since this experiment involved a large number of samples being analyzed in parallel, the cells were fixed in 4% paraformaldehyde for 30 minutes on ice prior to exposure to the immunoadhesin. The cells were then incubated with an FITC-conjugated antibody specific for rabbit IgG and the amount of binding determined as described in “Materials and methods.” MFI of HTSU-IgG binding minus MFI of SUA-IgG binding is plotted on the y-axis and the concentration of HTSU-IgG on the x-axis. Data are a representative experiment of 3 performed.