(A) Human IgM (left) and IgG (right) antibody binding to wild-type (WT), Gal knockout (GTKO), Gal/Sda double-knockout (GTKO/β4GalKO), and Gal, Sda, Neu5Gc triple-knockout (GTKO/β4GalKO/CMAHKO) pig red blood cells (pRBCs). Binding to TKO pig RBCs was not significantly different from human IgM and IgG binding to human RBCs of blood type O. (B) Pooled human serum complement-dependent cytotoxicity (hemolysis) to WT, GTKO, double-knockout, and triple-knockout pig RBCs. Cytotoxicity of the same serum to autologous human O RBCs was tested as a control. (C) Human T cell proliferative response to WT, GTKO/hCD46, and GTKO/hCD46/CMAHKO pig peripheral blood mononuclear cells (PBMCs) in mixed leukocyte reaction. (Triple-knockout pig PBMCs were not available to us at the time.)