title: Effects of alloantibodies to human leukocyte antigen on endothelial expression and serum levels of thrombomodulin.
abstract: Essentials The effect of alloantibodies on the endothelial expression of thrombomodulin is unknown. Thrombomodulin was quantified in stimulated endothelial cells and measured in serum samples. Anti-human leukocyte antigen (HLA) I vs. II antibodies have different effects on thrombomodulin. Anti-HLA II antibodies may promote a prothrombotic state and contribute to microangiopathy.
  
  
  
  Rationale Thrombomodulin (TBM) is an anticoagulant and anti-inflammatory transmembrane protein expressed on endothelial cells. Donor-specific alloantibodies, particularly those against human leukocyte antigen (HLA) class II, are associated with microvascular endothelial damage in solid allografts. Objective Our aim was to characterize the effects of anti-HLA antibodies on endothelial expression of TBM, and in particular, the differential effects of anti-HLA class I compared with those of anti-HLA class II. Methods We used human glomerular microvascular endothelial cells to examine TBM expression on anti-HLA-treated cells, and we tested sera from transplant recipients for soluble TBM. Results We found that whereas membrane TBM expression increased in a dose-dependent manner in the presence of anti-HLA class I antibodies, treatment with anti-HLA class II led to minimal TBM expression on the endothelial surface but to a cytosolic accumulation. Platelet adhesion studies confirmed the functional impact of anti-HLA class II. Quantitative densitometry of the membrane lysates further suggested that anti-HLA class II impairs TBM glycosylation. Furthermore, we found a significant association between the presence of circulating anti-HLA class II antibodies in transplant recipients and low serum levels of TBM. Conclusion These results indicate that ligation of anti-HLA class I and II antibodies produces different effects on the endothelial expression of TBM and on serum levels of TBM in transplant recipients. Anti-HLA class II antibodies may be associated with a prothrombotic state, which could explain the higher occurrence of microangiopathic lesions in the allograft and the poor outcomes observed in patients with these alloantibodies.
authors.affiliation: Transplantation Unit, Renal Division, Department of Medicine, University Health Center of Quebec, Faculty of Medicine, Laval University, Quebec City, QC, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Béland
authors.affiliation: Transplantation Unit, Renal Division, Department of Medicine, University Health Center of Quebec, Faculty of Medicine, Laval University, Quebec City, QC, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Vallin
authors.affiliation: Transplantation Unit, Renal Division, Department of Medicine, University Health Center of Quebec, Faculty of Medicine, Laval University, Quebec City, QC, Canada.
authors.forename: O
authors.initials: O
authors.lastname: Désy
authors.affiliation: Hematology and Oncology Division, Department of Medicine, University Health Center of Quebec, Faculty of Medicine, Laval University, Quebec City, QC, Canada.
authors.forename: E
authors.initials: E
authors.lastname: Lévesque
authors.affiliation: Transplantation Unit, Renal Division, Department of Medicine, University Health Center of Quebec, Faculty of Medicine, Laval University, Quebec City, QC, Canada.
authors.forename: S A
authors.initials: SA
authors.lastname: De Serres
mesh_terms: D002478:Cells, Cultured; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism*; D006031:Glycosylation; D006084:Graft Rejection / Q000097:blood / Q000276:immunology; D006085:Graft Survival; D006680:HLA Antigens / Q000276:immunology*; D006801:Humans; D007518:Isoantibodies / Q000276:immunology*; D007678:Kidney Glomerulus / Q000098:blood supply*; D016030:Kidney Transplantation / Q000009:adverse effects; D055806:Microvessels / Q000276:immunology* / Q000378:metabolism*; D010973:Platelet Adhesiveness; D011446:Prospective Studies; D018180:Thrombomodulin / Q000097:blood*; D013997:Time Factors
chemical_list: D006680:HLA Antigens; D007518:Isoantibodies; C546931:THBD protein, human; D018180:Thrombomodulin
keywords: alloantibodies; endothelial cells; thrombomodulin; thrombosis; transplantation