Figure 4.In vivo stimulation of human or baboon PBMC with anti-CD28 mAbs in NSG mice. One representative flow cytometry analysis (upper panel) and quantification of engraftment (low panel) of (A) human (n = 20) and (B) baboon (n = 18) cells in NSG mice two weeks after PBMC transfer. Each mark represents an individual mouse. (C, D) Percentage of activated human and baboon T lymphocytes expressing CD25 and CD69 among CD3⁺ cells in recipient blood and spleen 48 h after drug injection. Two weeks after PBMC transfer, mice received either 50 µg i.p. of superagonist anti-CD28 ANC28.1 mAb (red square symbols; n = 5 for human and n = 7 for baboon), 150 µg of humanized pegylated Fab’ fragment FR104 (blue dots; n = 6 for human and n = 5 for baboon) or an equivalent volume of excipient (open diamond; n = 5 for human and baboon). Each symbol represents an individual mouse. Horizontal bars indicate the mean. (E) Human and (F) baboon cytokine release after treatment in same experiments as in C and D; data are means ± SEM.*P < 0.05 and **P < 0.01 compared with control conditions. Cumulative data were obtained from three independent series of experiments using three different human and three baboon blood donors.