Hoskins L C, Larson G, Naff G B
Department of Medicine, Veterans Affairs Medical Center, Cleveland, Ohio, USA.
Transfusion. 1995 Oct;35(10):813-21. doi: 10.1046/j.1537-2995.1995.351096026361.x.
Epitopes of blood group A antigen can be enzymatically cleaved from red cells (RBCs), but the extent of cleavage required for normal survival in allogeneic blood transfusion recipients is unknown. Therefore, the cleavage rates were studied for A antigen epitope binding of 1) complement-activating anti-A, 2) Dolichos biflorus anti-A, lectin, and 3) hemagglutinating anti-A during incubation with a purified alpha-N-acetylgalactosaminidase, E.C. 3.2.1.49 (alpha-GalNAc'ase).
Suspensions of group A RBCs were incubated with alpha-GalNAc'ase. Cells were removed at intervals, washed, and tested for loss of binding by monoclonal, polyclonal, and complement-activating anti-A, D. biflorus anti-A1 lectin, and Ulex europaeus anti-H lectin.
A epitopes binding D. biflorus lectin were highly susceptible to alpha-GalNAc'ase; simultaneously with their loss, binding with U. europaeus lectin emerged. Loss of complement-mediated hemolysis was slower. A epitopes binding hemagglutinating anti-A were most resistant. Cleavage of A epitopes from membrane glycosphingolipids with short oligosaccharide chains was similarly resistant. Rates of cleavage from A1 and A2 RBCs were similar.
RBC epitopes of blood group A differ in susceptibility to cleavage and biologic reactivity, which suggests that subsets mediating important biologic functions exist on functionally and topographically distinct membrane glycoconjugates.
血型A抗原的表位可通过酶法从红细胞（RBC）上裂解下来，但在同种异体输血受者中正常存活所需的裂解程度尚不清楚。因此，研究了在与纯化的α-N-乙酰半乳糖胺酶（E.C. 3.2.1.49，α-GalNAc酶）孵育期间，1）补体激活抗A、2）双花扁豆抗A凝集素和3）血凝抗A与A抗原表位结合的裂解率。
将A型RBC悬液与α-GalNAc酶孵育。每隔一段时间取出细胞，洗涤，并检测单克隆、多克隆和补体激活抗A、双花扁豆抗A1凝集素和欧洲荆豆抗H凝集素结合的丧失情况。
与双花扁豆凝集素结合的A表位对α-GalNAc酶高度敏感；随着它们的丧失，与欧洲荆豆凝集素的结合出现。补体介导的溶血丧失较慢。与血凝抗A结合的A表位最具抗性。从具有短寡糖链的膜糖鞘脂上裂解A表位同样具有抗性。从A1和A2 RBC上的裂解率相似。
血型A的RBC表位在裂解敏感性和生物学反应性方面存在差异，这表明介导重要生物学功能的亚群存在于功能和拓扑结构不同的膜糖缀合物上。
