Presented at:
7th Trends in Immunosuppression
Berlin, Germany, February, 2006
Efficacy of Indirect pathway antigen processing and allorecognition
Stevenson S, Jiang S, Hernandez-Fuentes M, Lombardi G, Barber L, Lechler RI
King’s College London School of Medicine, London, UK; Anthony Nolan Research Institute, The Royal Free Hospital, London, UK
The uniquely strong primary alloresponse is due to the direct pathway of allorecognition which causes acute rejection. In contrast, the indirect pathway is characterised by an initial low frequency of T cells, which persist and expand because of continuous recipient APC trafficking through the graft causing chronic rejection. T cells with indirect specificity are the main targets for clinical tolerance, increasing long-term graft survival. To block the indirect pathway of allorecognition, we need to understand the molecular basis of indirect allo-antigen processing and presentation.
A CD4+ T cell line with indirect allo-specificity for HLA-A*0201 103-120 and restricted by HLA-DRB1*0101 was generated using autologous DCs pulsed with allopeptide. The allospecificity of this T cell line was assessed using one of the few MHC class II tetramers expressing A2 in the context of DR1.
DCs from an HLA-DRB1*0101 individual were incubated with different HLA-A*0201 preparations: peptide A2(103-120), soluble HLA-A*0201, HLA-A*0201 membrane preparation, necrotic and apoptotic HLA-A*0201 APC. Co-expression of DR and the A2-DR1 complex was evaluated comparing mAbs specific for DR and the complex. The most efficient way to generate the A2-DR1 complex was feeding with membrane preparation. Staining data correlates with preliminary data obtained using the line. These reagents should enable us to dissect the efficiency of class II restricted alloantigen presentation and the intracellular pathways of antigen processing for the indirect presentation of allo-antigens.
These results have important implications in the clinic: assay design to monitor the risk of chronic allograft nephropathy and potential novel therapeutic targets.