The pro-inflammatory cytokine TNF -a. and the immunoregulatory cytokine IL-IO have been implicated in acute rejection of kidney allografts. Similarly, the pro-fibrotic cytokine TGF-IJ 1 has been reported to be involved in the development of chronic rejection. It has also been shown that polymorphisms in the TNFA gene promoter (position -308) and in the TGF-IJI gene (at codon 25) correlate with differential production of these cytokines in vitro. Gene polymorphisms in the IL-IO promoter were also identified previously. However, their function had not been determined. Therefore, the initial part of this study was to investigate the effect of the three single base substitutions (G/A, CIT and CIA) in the IL-IO gene promoter on IL-IO gene expression. The results show that the G/A polymorphism at position -1117 of the a- 10 promoter was associated with differential production of IL-IO in vitro. Homozygous inheritance of a 'G' at this position correlated with a significant increase in the production of IL-IO by Con-A stimulated PBMCs. In addition, a-to gene reporter assays performed in the U937 monocytic cell line demonstrated that the activity of IL-l 0 promoter constructs containing the '0' was significantly higher than constructs containing the 'A' at position -1117 when co-transfected with an Ets-l transcription factor expression vector. Results from gel shift assays suggest that this difference in gene expression may be due to altered binding affinities of transcription factors to the IL-IO promoter. The second part of this study was to determine whether the IL-IO gene polymorphism, together with the TNF-a and TGF-pl gene polymorphisms, could influence the incidence and severity of acute rejection in the first 6 months following renal transplantation. Their effect on chronic transplant dysfunction was also assessed. The cytokine genotypes of 115 consecutive first cadaveric kidney allograft recipients and their corresponding donors were screened. Acute rejection episodes (RE) and the incidence of chronic transplant nephropathy (CTN) were defined clinically and confirmed histologically where possible. RE were further classified according to severity (RS), namely steroid resistant or responsive RE. The patients were categorised as high or low producers of the respective cytokines according to their genotypes and these were then correlated with the RE, RS and CTN. The recipient TNF-a high and IL-IO high producer genotype was significantly associated with multiple RE (~) in HLA-DR mismatched transplants (p=O.0047 and p=O.04S respectively) while only the TNF-a high producer genotype was associated with steroid resistant RE (p=O.02S). Donor cytokine genotypes did not correlate with RE or RS. When cytokine genotype combinations were analysed in context ofHLA-DR mismatching, the recipient T'NF-ahigh/donor TGF-Pl high producer genotype was associated with an increase in the incidence of RE. The recipiem TNF-a higML-lO high producer genotype was associated with an increase in the incidence of multiple RE in HLA-DR mismatched transplants and was also associated with steroid resistant RE. There was no significant association between cytokine genotypes and CTN. In conclusion, cytokine gene polymorphisms are determinants of RE and RS following kidney transplantation. Routine screening of these gene polymorphisms may have a clinical role in identifying patients at risk of multiple RE and severe rejections.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:488310 |
| Date | January 1999 |
| Creators | Sankaran, David |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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