Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Xenotransplantation. 2010 May-Jun;17(3):197-206. doi: 10.1111/j.1399-3089.2010.00579.x.
The continued presence of a primate antibody-mediated response to cells and organs from alpha1,3-galactosyltransferase gene-knockout (GTKO) pigs indicates that there may be antigens other than Gal alpha 1,3Gal (alpha Gal) against which primates have xenoreactive antibodies. Human and baboon sera were tested for reactivity against a panel of saccharides that might be potential antigen targets for natural anti-non-alpha Gal antibodies.
Human sera (n = 16) and baboon sera (n = 15) of all ABO blood types were tested using an enzyme-linked immunoadsorbent assay for binding of IgM and IgG to a panel of synthetic polyacrylamide-linked saccharides (n = 15). Human sera were also tested after adsorption on alpha Gal immunoaffinity beads. Sera from healthy wild-type (WT, n = 6) and GTKO (n = 6) pigs and from baboons (n = 4) sensitized to GTKO pig organ or artery transplants (of blood type O) were also tested. Forssman antigen expression on baboon and pig tissues was investigated by immunohistochemistry.
Both human and baboon sera showed high IgM and IgG binding to alpha Gal saccharides, alpha-lactosamine, and Forssman disaccharide. Human sera also demonstrated modest binding to N-glycolylneuraminic acid (Neu5Gc). When human sera were adsorbed on alpha Gal oligosaccharides, there was a reduction in binding to alpha Gal and alpha-lactosamine, but not to Forssman. WT and GTKO pig sera showed high binding to Forssman, and GTKO pig sera showed high binding to alpha Gal saccharides. Baboon sera sensitized to GTKO pigs showed no significant increased binding to any specific saccharide. Staining for Forssman was negative on baboon and pig tissues.
We were unable to identify definitively any saccharides from the selected panel that may be targets for primate anti-non-alpha Gal antibodies. The high level of anti-Forssman antibodies in humans, baboons, and pigs, and the absence of Forssman expression on pig tissues, suggest that the Forssman antigen does not play a role in the primate immune response to pigs.
灵长类动物对基因敲除（GTKO）猪的细胞和器官仍存在抗体反应，这表明可能存在除 Gal alpha 1,3Gal（αGal）之外的抗原，灵长类动物对其具有异种反应性抗体。本文检测了人血清和狨猴血清对一组可能是天然抗非-αGal 抗体的潜在抗原靶标的糖的反应性。
采用酶联免疫吸附试验（ELISA）检测了 16 例不同 ABO 血型的人血清和 15 例狨猴血清中 IgM 和 IgG 与一组合成的聚丙烯酰胺连接的糖（n=15）的结合情况。还对经过αGal 免疫亲和珠吸附的人血清进行了检测。还检测了来自健康的野生型（WT）和 GTKO（n=6）猪以及对 GTKO 猪器官或动脉移植（血型 O）致敏的狨猴（n=4）的血清。通过免疫组化法检测了狨猴和猪组织中的 Forssman 抗原表达情况。
人血清和狨猴血清均显示出对αGal 糖、α-乳糖胺和 Forssman 二糖的高 IgM 和 IgG 结合。人血清还显示出对 N-乙酰神经氨酸（Neu5Gc）的适度结合。当人血清经αGal 低聚糖吸附后，与αGal 和α-乳糖胺的结合减少，但与 Forssman 结合未减少。WT 和 GTKO 猪血清均对 Forssman 有高结合，GTKO 猪血清对αGal 糖有高结合。对 GTKO 猪致敏的狨猴血清对任何特定糖均无明显增加的结合。狨猴和猪组织的 Forssman 染色均为阴性。
我们无法明确鉴定出所选糖组中任何可能是灵长类动物抗非-αGal 抗体靶标的糖。人类、狨猴和猪体内高抗 Forssman 抗体水平，以及猪组织上缺乏 Forssman 表达，提示 Forssman 抗原在灵长类动物对猪的免疫反应中不起作用。
