Spontaneous and therapeutic glycosidic accommodation of host and graft in ABO(H)-incompatible transplantation, a hypothesis.

In contrast to non-nucleated ABO(H) red cells, which when transfused to a blood group O(H) recipient undergo destruction within minutes, such hyperacute, humoral rejection occurs relatively rare in transplantations of highly nucleated, metabolically active solid organs; it is extremely rare in liver transplantations (Adams, 1991) (Della-Guardia et al., 2008) and does not occur in successful bone marrow engraftment (Takahashi, 2005). Moreover, a case of transient, selective disappearance of preexisting donor-specific HLA-antibodies after an incompatible liver transplantation, without any rejection episodes, has been reported by Bastiani (Bastani, 2006), and according to Taner et al. (2014)<i> </i>such transient decrease of donor-specific HLA-antibodies is not uncommon after incompatible liver transplantation. Treatment of pure red cell aplasia (PRCA) with ABO incompatible RBC, after ABO blood group incompatible hematopoietic stem cell transplantation, was followed by spontaneous decrease of isoagglutinin levels in several individuals (Stussi et al. 2009). In addition, an exponential fall in both anti-A/B reactive IgM and IgG titers was observed after ABO(H) incompatible bone marrow transplantation (Rowley et al. 2000; Lee et al. 2003). These phenomena in “major incompatibilities” most likely reflect a complex mechanism, in which pre-existing anti-graft-reactive immunoglobulins of the host are adsorbed on complementary sites on the cell surfaces of the graft, but unlike on the surfaces of metabolically weak red cells, appear to be completed by graft-phenotype-specific protective glycosylation and may only recover when the graft-intrinsic enzymatic power and supply of specific substrates are exhausted.

与无核ABO(H)红细胞（non-nucleated ABO(H) red cells）不同，后者输注至O(H)血型受血者体内后可在数分钟内被破坏；这类超急性体液排斥反应（hyperacute, humoral rejection）在高核化、代谢活跃的实体器官移植中相对少见，在肝移植（liver transplantations）中极为罕见（Adams, 1991；Della-Guardia等, 2008），而在成功的骨髓植入（bone marrow engraftment）中则不会发生（Takahashi, 2005）。此外，Bastiani曾报道1例不相容性肝移植术后出现预先存在的供者特异性HLA抗体（donor-specific HLA-antibodies）一过性选择性消失，且未发生任何排斥事件（Bastani, 2006）；据Taner等（2014）报道，不相容性肝移植术后供者特异性HLA抗体的此类一过性下降并不少见。在ABO血型不相容造血干细胞移植（hematopoietic stem cell transplantation）后，采用ABO血型不相容红细胞治疗纯红细胞再生障碍性贫血（pure red cell aplasia, PRCA）的多名患者中，均出现了同种凝集素（isoagglutinin）水平自发下降的情况（Stussi等, 2009）。另有研究显示，ABO(H)不相容骨髓移植术后，抗A/B反应性IgM与IgG滴度（anti-A/B reactive IgM and IgG titers）均出现指数下降（Rowley等, 2000；Lee等, 2003）。上述“主要不相容性”（major incompatibilities）相关现象很可能反映了一种复杂机制：宿主预先存在的抗移植物反应性免疫球蛋白（anti-graft-reactive immunoglobulins）结合于移植物细胞表面的互补位点，但与代谢活性较弱的红细胞表面不同，此类免疫球蛋白似乎可通过移植物表型特异性的保护性糖基化（graft-phenotype-specific protective glycosylation）被清除，且仅当移植物自身的酶活性（graft-intrinsic enzymatic power）与特异性底物供给耗尽时，该免疫球蛋白水平才会恢复。