From what I have read tolerance is more likely to be achieved in liver transplantation than it is in transplantation of other organs.
With that in mind I am nevertheless posting the following articles which involve renal transplantation. The reason is to attempt to address your question:
"Back to the point of my ponderings...was whether genetically similar tissue would decrease the rate of rejection, or increase the chances of weaning, or not experiencing rejection, and the last study you posted seem to agree at least that the greater the genetic similarity the better chances for the patient."
I think that this issue is far too complex to make broad sweeping assertions regarding transplant outcome based on genetic similarity. I believe these articles reflect the complexity of this subject.
The Role of Donor-Recipient Relationship in Long-Term Outcomes of Living Donor Renal Transplantation.
Miles CD, Schaubel DE, Liu D, Port FK, Rao PS.
1 Department of Medicine, Nebraska Medical Center, Omaha, NE. 2 Department of Biostatistics, University of Michigan, Ann Arbor, MI. 3 Scientific Registry of Transplant Recipients, Ann Arbor, MI. 4 Arbor Research Collaborative for Health, Ann Arbor, MI. 5 Department of Medicine, University of Michigan, Ann Arbor, MI.
BACKGROUND.: Graft failure related to acute and chronic rejection remains an important problem in transplantation. An association has been reported between microchimerism and the development of tolerance. Since it has been established that cells of fetal origin can be found in maternal tissues long after parturition, and cells of maternal origin may persist for years in offspring, we hypothesized that this fetal-maternal microchimerism may confer tolerance and thus less graft loss for kidneys transplanted between mothers and their offspring. METHODS.: We used data from the Scientific Registry of Transplant Recipients to compare death-censored graft survival among recipients of living-related renal transplants sharing at least one human leukocyte antigen (HLA) haplotype with their donor. A total of 23,064 such transplants were reported from 1995 to 2004. A Cox proportional hazards model was constructed to compare death-censored graft survival among the following donor-recipient pairings: child-to-mother, child-to-father, mother-to-child, father-to-child, 1-haplotype matched siblings, and HLA-identical siblings. RESULTS.: HLA-identical sibling recipients had the best survival, but results for the child-to-father group were not significantly worse (hazard ratio=1.07, P=0.47). Mother-to-child transplants had the poorest graft survival (hazard ratio=2.61, P<0.0001). We found no evidence of tolerance to kidneys transplanted between mothers and offspring. CONCLUSIONS.: Our analysis of 1-haplotype matched living-related renal transplants argues against tolerance to organs based on fetal-maternal microchimerism. Mechanistic studies examining the relationship between chimerism and immune sensitization would be useful to explore our results, and may contribute to a better understanding of tolerance.
Nephrol Ther. 2008 Feb;4(1):72-6.Click here to read Links
[Transplantation from a living related donor: Results]
[Article in French]
Hourmant M, Kolko A.
Service de néphrologie et d'immunologie clinique, CHU de Nantes, 44093 Nantes cedex, France. [email protected]
The results of transplantation from a living donor (LDT) are constantly better than those of cadaveric transplantation (2004 Report of the French Agency of Biomedicine: graft survival 80 versus 63% at 10 years). Transplantation from an HLA-identical sibling is in any case the best combination, but there is no significant difference in graft survival when the donor is a parent, a child, a non HLA-identical sibling, a spouse or an unrelated person. The reasons for these better results are several: the quality of the kidney transplant, the absence of brain death, the advantage of a programmed surgery and of preemptive transplantation. It is admitted now that HLA compatibility plays a minor role. As in cadaveric transplantation, acute rejection, delayed graft function, pretransplant HLA immunisation, age of the donor and the recipient and possibly the discrepancy between the weight of the donor and the recipient are determinants of transplant outcome.
1: Transplantation. 2007 Oct 27;84(8):972-80.Click here to read Links
Parental donors in live-donor kidney transplantation associated with increased rejection rates and reduced glomerular filtration rates.
Lim WH, Chang SH, Coates PT, McDonald SP.
Department of Renal Medicine, Sir Charles Gairdner Hospital, Western Australia, Australia. wai.***@****
BACKGROUND: Living unrelated and related kidney transplantation has been shown to have similar allograft survival. However, the effect of donor-recipient relatedness in living-related and unrelated kidney transplantation on graft and patient survival remains uncertain. METHODS: Using Australia and New Zealand Dialysis and Transplant Registry, primary living renal transplant recipients in Australia between 1995 and 2004 were studied (n=1989). Donors were categorized according to their relationship with recipients: parent (n=606), child (n=103), spouse (n=358), sibling (n=656), other living-related donors (n=81), and other living-unrelated donors (n=185). Outcomes analyzed included the presence of rejection at 6 months, estimated glomerular filtration rate (eGFR) at 1 and 3 years, graft survival, and patient survival. RESULTS: A greater proportion of renal transplant recipients from parental and spousal donors were transplanted preemptively. Donor groups had no relationship with graft or patient survival. Parental donors were associated with an increased relative odds of acute rejection (odds ratio 1.69, 95% confidence interval 1.13-2.53, P=0.009) and a lower eGFR at both 1 and 3 years (coefficient -2.99 and -5.68, respectively; P<0.0001) compared to other donor groups (reference sibling donor group). CONCLUSIONS: This study has established that donor-recipient relatedness in both related and unrelated living kidney transplantation had no significant effect on graft and patient survival. Parental donors were associated with a higher relative risk of rejection and lower eGFR in the transplant recipients, although these findings did not translate to a worse graft outcome.