Fig. 2

Xenograft activates the complement system. The binding of IgG/IgM to the protein α-Gal on the graft surface activates the classical pathway of complement, while the interaction of IgA with α-Gal activates the alternative pathway. The combined activation of classical and alternative pathways leads to the generation of C5 convertase, ultimately resulting in the formation of the membrane attack complex (MAC) composed of C5b, C6, C7, C8, and C9. This MAC complex functions to attack the xenograft