Complement regulation in the GalT KO era.
A number of institutes have reported on the successful production of alpha-galactosyltransferase knockout (GalT-KO) pigs. After producing such pigs, hyperacute rejection appeared to no longer be a problem. However, acute vascular rejection (AVR)/acute humoral xenograft rejection (AHXR) is defined as a rejection that begins within 24 h after transplantation and gradually destroys the graft. The origin of AVR/AHXR continues to be a controversial topic, but is generally thought to be initiated by xeno-reactive antibodies, including non-Gal antibodies and subsequent activation of the graft endothelium, the complement and the coagulation systems. The complement is activated via the classical pathway by non-Gal antigens and ischemia-reperfusion injury, via the alternative pathway, especially on islets, and via the lectin pathway. Therefore the complement system is still an important recognition and effector mechanism of AVR/AHXR. In addition, quite recently, based on the relationship between complement and coagulation systems, a new pathway has been proposed. All complement regulatory proteins (CRPs) have the ability to regulate complement activation in different ways. Therefore, to effectively protect xenografts against AVR/AHXR, it appears reasonable to employ not only one but several CRPs including anti-complement drugs. Non-Gal antigens, such as the Hanganutziu-Deicher antigen, is still present on GalT-KO grafts. The further assessment of antigens continues to be an important issue in the area of clinical xenotransplantation. The above conclusions suggest that the expression of human CRPs on GalT-KO grafts is necessary. Moreover, multilateral inhibition of complement activation is required in conjunction with the regulation of the coagulation system.
Miyagawa
Shuji
S
Division of Organ Transplantation, Department of Surgery, Osaka University Graduate School of Medicine, Osaka, Japan. miyagawa@orgtrp.med.osaka-u.ac.jp
Yamamoto
Aki
A
Matsunami
Katsuyoshi
K
Wang
Dandan
D
Takama
Yuichi
Y
Ueno
Takehisa
T
Okabe
Masaru
M
Nagashima
Hiroshi
H
Fukuzawa
Masahiro
M
D000818:Animals; D030801:Animals, Genetically Modified; D003167:Complement Activation / Q000276:immunology; D003165:Complement System Proteins / Q000276:immunology*; D005700:Galactosyltransferases / Q000235:genetics / Q000276:immunology; D006084:Graft Rejection / Q000276:immunology; D006801:Humans; D014183:Transplantation, Heterologous / Q000276:immunology
D003165:Complement System Proteins; D005700:Galactosyltransferases; C047006:N-acetyllactosaminide alpha-1,3-galactosyltransferase