Morphologic and functional features of human platelets induced by NIP-004 in NOG mice. (A) Immunoelectron microscopy using antibody against HuCD41a identified human platelets in PRP derived from NIP-004–treated mice. The surface of a platelet located in the center is labeled with gold particles (arrow), indicating that it is of human origin. Bar, 1 μm. (B) P selectin (HuCD62p) expression upon ADP stimulation in human platelets was similarly increased in both vehicle- and NIP-004–treated mice. (C) After stimulation with various concentrations of ADP, there was a similar dose-dependent escalation in the percentage of PAC-1–positive human platelets from vehicle- and NIP-004–treated NOG mice receiving xenotransplants. PAC-1 antibody specifically recognizes the activated form of GPIIbIIIa. Data are expressed as the mean ± SEM (n = 4).