Role Of IgG In Avxr

While IgM is often the more significant preformed primate xenoantibody, IgG becomes more prominent following exposure to porcine antigens. While IgM titers rise and fall, IgG titers undergo a more significant and sustained increase, likely representing an isotype switch. Exposure of humans to vascularized porcine organs also results in a rise and fall in IgM, and a sustained IgG rise. Since their functional avidities for aGal are similar, an increasing IgG:IgM ratio will also result in fewer antigenic sites bound by IgM. This results in a relative decrease in complement activating potential since IgGs are less efficient than IgM at fixing complement. Infusion of human IgGs into primate recipients of porcine cardiac xenografts has been shown to prevent HAR, presumably by successful competition with IgM for endothelial binding sites although other mechanisms may also contribute.

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