All five baboons (B158, B156, B265, B270 and B284) used in this study, had low levels of anti- non-Gal IgG pre-transplant. Pre transplant anti-non-Gal IgG levels from baboons 167 and 175, are shown to demonstrate the varying levels of pre-transplant IgG in baboons available to us. The positive control sera were from a baboon that was known to be sensitized to pig and the background is shown using secondary goat anti-human IgG.