Anti-H can trigger apoptosis and down-regulate FUT1 expression in erythroid differentiated K562 cells without complement mediation

The reason why delayed RBC engraftment and pure red cell aplasia (PRCA) develop only in some but not all recipients of major ABO-incompatible hematopoietic stem cell transplantation (HSCT) remains elusive and the underlying mechanisms are not fully understood. Understanding how incompatible erythroid blood group antibodies (Abs) interact with ABH antigens (Ags) of grafts, and investigating how to induce artificially accommodation of grafts are of obvious importance in transplantation immunology. The effects of anti-H on proliferation, apoptosis, and α-(1,2)-fucosyltransferase gene (FUT1) expression in erythroid differentiated K562 cells were analyzed by the MTT assay, Annexin V/PI staining, and quantitative RT-PCR method. The growth of erythroid differentiated K562 cells was significantly suppressed when anti-H dilution was ≤ 1:8 (P<0.001, as compared with 1:16). Under the complement-free culture conditions, the apoptotic ratio of erythroid differentiated K562 cells was significantly increased when anti-H dilution was ≤ 1:16 (P<0.05, as compared with 1:32). The apoptosis was not only closely associated with anti-H dilution (F=138.991, P<0.001), but also correlated with treated time (F=583.249, P<0.001), which indicated typical dose- and time-dependent effects. Under the complement-free culture conditions, the FUT1 mRNA expression level was also suppressed when anti-H dilution was ≤ 1:16 (P<0.05, as compared with 1:32), which also manifested in typical dose-dependent (F=130.356, P<0.001) and time-dependent (F=1432.00, P<0.001) effects. The results confirm that anti-H can trigger apoptosis and down-regulate FUT1 expression in erythroid differentiated K562 cells without complement mediation. The findings suggest that anti-H could accommodate grafts through triggering apoptosis and down-regulating Fut1 expression to reduce ABH antigens.

Decrease of blood type antigenicity over the long-term after ABO-incompatible kidney transplantation

BACKGROUND

Few studies have investigated the changes in the antigenicities of the transplanted organs after transplantation.

METHODS

We examined, by immunohistochemical assay, the changes in expression of the blood-type antigens on the transplanted kidneys over the long-term after ABO-incompatible kidney transplantation with A- or B-antigen incompatibility (blood type A to B and B to A). The subjects were six patients, including one case with graft loss, who had received ABO-incompatible kidney allografts more than ten years previously. As normal controls, four cases of ABO-compatible transplantation during the same period, including two recipient/donor pairs each with blood group A1 and blood group B were enrolled.

RESULTS

Expression of the blood-type A or B antigens decreased gradually to 91.8% during the first three months after transplantation, 85.8% during the first five years, 64.1% during the first ten years, and 57.6% over ten years after transplantation on average in ABO-incompatible transplant recipients. In one patient with graft loss due to severe antibody-mediated rejection, the donor's type B blood-type antigens on the transplanted graft had changed but partially to the recipient's blood-type A antigen by 2582days after the transplantation, suggestive of the occurrence of blood-type chimerism on the endothelium. In ABO-compatible transplant recipients, such changes in expression were not observed. The average percentage of blood-type antigen-positive vessels at more than ten years after the renal transplantation was 99.8%.

CONCLUSIONS

Decrease in the expression of the donor's blood-type antigen on the endothelium of the graft has been considered as one of the mechanisms underlying the accommodation occurring over the long-term after ABO-incompatible kidney transplantation. On the other hand, establishment of antigenic chimerism on the graft endothelium could be one of the hallmarks of the immunological reaction associated with antibody-mediated rejection.