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Title: The role of HLA-DP in renal transplantation
Author: Barker, Anna
ISNI:       0000 0001 2417 8629
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2008
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Introduction: HLA-DP (DP) is a human Major Histocompatibility Complex class II molecule which presents peptide to the immune system. In the context of kidney transplantation, DP mismatches (mm) can be recognised as allogeneic, demonstrated by the detection of DP specific antibodies (abs). IFN-y is produced during the inflammatory response following kidney transplantation and induces cell surface expression of HLA-c1ass II molecules, providing non-self target molecules for the binding of abs and subsequent graft damage. This study aimed to address the hypotheses that DP mm affect kidney transplant (tx) survival, DP abs are produced. against mismatched donor antigens and are clinically relevant, DP expression can be upregulated in cell types involved in tx rejection and binding of abs to class II molecules leads to the activation of cell signalling pathways which contribute to the mechanism of chronic rejection (CR). Methods: 147 recipients of txs with zero mms at HLA-A, B and DR (000 txs) were DPB1 typed and 127 were DPA1 typed. The effect of mismatching at both loci was investigated using Kaplan-Meier survival analysis and multivariate Cox proportional hazards analysis. 123 of the recipients were tested for class II and DP abs using FlowPRA® assays (One Lambda) and their clinical significance analysed. HLA-DPA1 and B1 gene expression was investigated in IFN-y treated Human Microvascular Endothelial Cells (HMEC) and HK-2 cells (a renal epithelial cell line) using quantitative real-time reverse transcriptase PCR (q r-t RT-PCR). The effect of IFN-y treatment on HMEC DP cell surface expression was determined using flow cytometry. IFN-y-treated HMEC were investigated for cell activation in response to HLA ab binding using a plate fluorimetry method to detect changes in intracellular calcium levels ([Ca2+]i). HMEC protein expression in response to DP ab binding was investigated using an antibody array (Sigma). Results: DPA1 mm had no effect on graft survival whereas an effect of DPB1 mm was demonstrated in retransplant patients using Cox regression analysis (p = 0.04). DP abs were detected in 11 of 40 (27.5%) patients with class II abs. DP abs were frequently found in patients who had had more than one transplant (7/11) and in pre-ODD tx samples (10/11). Six of the 11 recipients had no DP mms at their 000 tx. DP abs were produced in response to previous transplant or pregnancy. The DP response was restimulated by repeat DP mm and in one case was implicated in tx rejection and in another with tx rejection and graft loss. DP gene and cell surface expression increased in response to IFN-y treatment. Cell activation measured by [Ca2+]i increase was observed after class I and class II ab binding. DP ab binding to HMEC led to increased expression of a variety of proteins inclUding those involved in apoptosis, cell cycle and signal transduction. Summary and Conclusion: This study has shown that DP does have a role in renal transplantation. DPB1 mms affect survival of re-transplants. DP abs are produced and reactivated in response to repeat DP mm and were implicated in graft loss. DP gene and cell surface expression was induced on epithelial and endothelial cell lines and DP ab binding led to cell activation. DP ligation on HMEC also led to increased expression of proteins previously shown to be involved in class I ab-mediated cell signalling pathways in endothelial cells. The results of this study suggest that all kidney tx candidates who have had a preVious transplant or pregnancy should be tested for DP abs in order to inform donor selection and patient management.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available