A sizzling（极热的） genetic² discovery by Chinese scientists may one day allow pig tissue to be transplanted successfully into humans. Their research presented in the Journal of Leukocyte Biology (http://www.jleukbio.org) represents a major step forward toward filling the shortage of vital organs for human transplantation. At the core of their work, they showed that altering or overexpressing the human programmed death ligand-1 (PD-L1) molecule³ in the endothelial cells（内皮细胞） of pig arteries⁴ reduces the conditions that lead to rejection⁵. This strongly suggests that humans could receive altered porcine（猪的） organs with fewer complications. "Genetically⁶ engineered pigs may someday overcome the severe donor⁷ organ shortage, and save human lives," said Qing Ding, Ph.D., co-study author from the Shanghai Institute of Immunology at the Shanghai Jiaotong University School of Medicine in Shanghai, China.

To make the discovery, scientists conducted experiments using two groups of pig vascular⁸（血管的） endothelial cells. The first group was genetically engineered to express human PD-L1, while the second group was normal. When both sets of cells were exposed to human lymphocytes（淋巴球） , lower rejection response occurred in the group with the altered gene¹, while higher rejection responses were seen in the normal cells. Study results suggest that human PD-L1 could be used as a novel therapeutic⁹ agent to enhance tolerance¹⁰ of xenotransplants（异种器官移植） and also supports the possibility of using human PD-L1 transgenic pigs as xenotransplant donors¹¹. Using this type of genetic engineering technique could potentially overcome current challenges related to successful pig/human transplant rejection.

"Xenotransplantation has the potential to fill a huge gap between the number of available human donor tissue and number of needy¹² recipients," said John Wherry, Ph.D., Deputy Editor of the Journal of Leukocyte Biology, "but our understanding of the pathways that might enhance the acceptance and physiological¹³ function of organs from animals such as pigs remains¹⁴ incomplete. The study by Dr. Ding and his colleagues is a very substantial step forward in defining a key immunoregulatory pathway that could be targeted in this setting."