ABO-incompatible renal transplantation: From saline flushes to antigen-specific immunoadsorption-Tools to overcome the barrier

On April 23, 1951, a 30-year-old woman received the first intentional ABOi (ABO incompatible) renal transplantation in Boston. At that time, it was commonly believed that intensely rinsing the graft to remove blood would be sufficient to overcome any immunological problems associated with blood type incompatibility. However, when the abovementioned patient and another ABOi transplant recipient died within a month, Humes and colleagues arrived at the same conclusion: "We do not feel that renal transplantation in the presence of blood incompatibility is wise." In the decades that followed, we learned that the oligosaccharide surface antigens representing the ABO-blood group antigens are expressed not only on erythrocytes but also on cells from various tissues, including the vascular endothelium. The growing gap between organ demand and availability has sparked efforts to overcome the ABO barrier. After its disappointing results in the early 1970s, Japan became the leader of this endeavor in the 1980s. All protocols are based on 2 strategies: removal of preformed antibodies with extracorporeal techniques and inhibition of ongoing antibody production. Successful ABOi renal transplantation became possible with the advent of splenectomy, new immunosuppressive drugs (e.g., rituximab, a monoclonal antibody against CD20), and extracorporeal methods such as antigen-specific immunoadsorption. This review summarizes the underlying pathophysiology of ABOi transplantation and the different protocols available. Further, we briefly touch potential short- and long-term problems, particularly the incidence of infectious complications and malignancies, that can arise with high-intensity immunosuppressive therapy

Increased risk of venous thrombosis by AB alleles of the ABO blood group and Factor V Leiden in a Brazilian population

Most cases of a predisposition to venous thrombosis are caused by resistance to activated protein C, associated in 95% of cases with the Factor V Leiden allele (FVL or R506Q). Several recent studies report a further increased risk of thrombosis by an association between the AB alleles of the ABO blood group and Factor V Leiden. The present study investigated this association with deep vein thrombosis (DVT) in individuals treated at the Hemocentro de Pernambuco in northeastern Brazil. A case-control comparison showed a significant risk of thrombosis in the presence of Factor V Leiden (OR = 10.1), which was approximately doubled when the AB alleles of the ABO blood group were present as well (OR = 22.3). These results confirm that the increased risk of deep vein thrombosis in the combined presence of AB alleles and Factor V Leiden is also applicable to the Brazilian population suggesting that ABO blood group typing should be routinely added to FVL in studies involving thrombosis

Cleavage of von Willebrand Factor by Granzyme M Destroys Its Factor VIII Binding Capacity

Von Willebrand factor (VWF) is a pro-hemostatic multimeric plasma protein that promotes platelet aggregation and stabilizes coagulation factor VIII (FVIII) in plasma. The metalloproteinase ADAMTS13 regulates the platelet aggregation function of VWF via proteolysis. Severe deficiency of ADAMTS13 is associated with thrombotic thrombocytopenic purpura, but does not always correlate with its clinical course. Therefore, other proteases could also be important in regulating VWF activity. In the present study, we demonstrate that VWF is cleaved by the cytotoxic lymphocyte granule component granzyme M (GrM). GrM cleaved both denaturated and soluble plasma-derived VWF after Leu at position 276 in the D3 domain. GrM is unique in that it did not affect the multimeric size and pro-hemostatic platelet aggregation ability of VWF, but instead destroyed the binding of VWF to FVIII in vitro. In meningococcal sepsis patients, we found increased plasma GrM levels that positively correlated with an increased plasma VWF/FVIII ratio in vivo. We conclude that, next to its intracellular role in triggering apoptosis, GrM also exists extracellularly in plasma where it could play a physiological role in controlling blood coagulation by determining plasma FVIII levels via proteolytic processing of its carrier VWF