P.M. van den Berg-Loonen

Functional versus structural matching: can the CTLp test be replaced by HLA allele typing?

Human leukocyte antigen (HLA) incompatibilities are the most important immunological barriers to bone marrow transplant success when using unrelated donors. Until recently, standards for donor selection included serological methods for HLA class I antigens and DNA-based typing for HLA class II alleles. In our center cytotoxic T-lymphocyte precursor (CTLp) assays have been an integrated part of the search selection procedure as well. More recently, DNA-based typing for HLA class I became available. This allowed us to determine the correlation of CTLp frequencies directed against incompatibilities at the HLA-A, -B, and -C locus in 211 donor-recipient pairs. HLA class I incompatibilities are significantly (p < 0.001) associated with high CTLp frequencies. Exceptions did occur, high CTLp frequencies are seen in 14% of the HLA-A, -B, and -C allele matched pairs, whereas in 7% of the pairs mismatched for HLA-A or -B a low CTLp frequency occurred. The successful outcome of transplants performed in the latter cases suggest that the CTLp test can be used as a tool to detect permissible mismatches when no fully matched donor is available. The influence of HLA-C mismatches on the CTLp outcome was less clear. Although in the majority of mismatched pairs (64%) the CTLp frequency was high, in 36% of the pairs the CTLp frequency was low. Analysis of HLA amino acid sequences was performed on the HLA-C allele mismatched group. An amino acid difference was always found at five polymorphic positions 97, 99, 113, 114, and 116 situated at the peptide binding groove in the high CTLp frequency group, whereas in the low CTLp frequency group this was observed in only 9 of 17 combinations (p < 0.001). However, this is mainly due to Cw*0303-0304 mismatches. In conclusion, although there is a highly significant correlation between the outcome of the CTLp frequency test and HLA allele class I typing, exceptions occur. It is unclear whether they are all clinically relevant but they certainly provide additional insight in allograft recognition.

Uniparental maternal disomy 6 in a renal transplant patient.

HLA analysis of the family of a renal transplant patient revealed an extremely rare condition. On repeated typings the only demonstrable HLA antigens shown in the propositus were from the maternal haplotype, HLA-A11,-B46,-CW1,-DR14,-DQ1. No paternal antigens could be demonstrated either by serologic or by DNA-typing methods. A paternity investigation was carried out to exclude the possibility of the legal father not being the biological father. The results of this investigation showed a paternity index I = > 20000 and a fatherhood probability W = > 99.995%. Karyotyping of the patient showed two normal chromosomes 6 and no other chromosomal abnormalities. Maternal isodisomy was demonstrated from the analysis of polymorphic DNA markers, involving the short as well as the long arm of chromosome 6. These data are consistent with this patient having the first uniparental maternal disomy 6 reported (inheritance of two identical chromosome 6 haplotypes from the mother and none from the father).

Kidney Transplantation Using Elderly Non‐Heart‐Beating Donors: A Single‐Center Experience

Although acceptable outcomes have been reported in both non‐heart‐beating (NHB) and elderly donors individually, the large pool of elderly NHB donors has not yet been fully utilized. In 1994, we expanded our transplant protocol to include NHB donors aged over 65 years and this study compares the clinical outcomes with regular NHB transplantations. Up to June 2005, 24 patients were transplanted at our center with kidneys from NHB donors aged 65 years or more, whereas 176 patients received grafts from conventional NHB donors during the same period. Grafts from older donors were associated with inferior glomerular filtration rates (29 vs. 44 mL/min after 1 year, p = 0.01) and graft survival (52% vs. 68% after 5 years, p = 0.19) compared to younger NHB donor grafts, although the difference in graft survival was not statistically significant. Exclusion of older NHB donor kidneys with severe vascular pathology resulted in similar graft survival of older and younger NHB donor kidneys. We conclude that the use of elderly NHB donors in order to expand the donor pool was associated with unacceptable clinical outcomes and cannot be justified without further refinement in their selection, for example, by histological assessment of pretransplant biopsies.

Risk factors for cytomegalovirus infection and disease in renal transplant recipients: HLA-DR7 and triple therapy

In a prospective study, an analysis of risk factors for the development of cytomegalovirus (CMV) infection and disease was performed on 77 renal allograft recipients. Twenty-five out of the 77 recipients (32%) had a CMV infection. Twenty-two of the recipients received triple immunosuppressive therapy (cyclosporin A, prednisolone, and azathioprine) while the remaining 55 received standard therapy (cyclosporin A and prednisolone). In 23 recipients (30%) acute rejection was diagnosed and the first positive parameter of infection occurred 22 days after rejection therapy. Infection occurred in 10 out of 18 HLA-DR7-positive recipients (56%) and in 15 out of 59 HLA-DR7-negative recipients (25%; P< 0.02). In multiple regression analysis, HLA-DR7 was found to be a significant predictor of CMV infection (P< 0.005). CMV disease was diagnosed in only 9 out of 25 recipients with an acute infection. Six recipients (67%) with CMV disease received triple therapy for maintenance immuuosuppression; this was significantly correlated to CMV disease (P< 0.05) as compared to three recipients (33%) with CMV disease maintained with standard therapy. Our data suggest that HLA-DR7-positive recipients are more susceptible to CMV infection and that CMV disease is associated with triple immunosuppressive therapy.

The influence of DR match of blood donor and recipient on the formation of T- and B-cell antibodies and on renal allograft outcome.

It has been shown that patients transfused with one unit of blood mismatched for both HLA DR antigens have an increased rate of formation of cytotoxic leukocyte antibodies compared to patients who received blood which differs in only one DR antigen. In the same study it was found that DR sharing of the blood transfusion donor and patient improved results of kidney and heart transplantation. However, the data were mostly collected in a retrospective manner and came from various centers. Furthermore, no information was available on whether these antibodies were directed to B- or T-cells. Therefore, the influence of DR match of recipient and blood donor on the formation of T- and B-cell antibodies as well as on clinical course after kidney transplantation was studied prospectively in patients transplanted in one centre.

Focal glomerulosclerosis in neonatal kidney grafts.

Two adult patients received both kidneys from neonatal donors. After grafting an accelerated growth of the kidneys was observed. Five weeks after transplantation the craniocaudal diameter had increased from 4 and 3.4 to 8.3 and 6.1 cm, respectively. Histological examination of the kidneys showed segmental glomerulosclerosis 24 and 3 months after grafting, respectively.

The impact of ischemic lesions in the donor kidney, donor age, recipient age and HLA (A, B, C, DR, DQ) matching on clinical course after kidney grafting

It is generally accepted that HLA matching improves graft survival. However, there is no consensus on whether this improvement is reflected on daily clinical course. Clinical course after renal transplantation depends on many factors, such as donor age, recipient age, ischemic score in the kidney, and HLA matching. The relative contribution of these factors is unknown. Because management of the recipients in the various centers differs considerably, only a single centre study would reveal the relative contribution of all these factors. Therefore, in our centre we studied the influence of these parameters on the clinical course after renal allografting.

Results of pancreas transplantation with irradiated spleen and segment of duodenum

At the introduction of our Pancreas Transplant Program in 1985, we decided to try to prevent graft thrombosis by including the spleen in the graft (1). In those days the incidence of graft thrombosis was as high as 25% (2). We based our policy on the work of Starzl (3), who introduced the inclusion of the spleen in pancreatic transplantation. The assumption is, that preservation of the normal vascular architecture of the pancreas will maintain the normal flow pattern. We presume that the pancreas receive about 1% of the heart minute volume and the spleen about 5%, and therefore, inclusion of the spleen might increase several times the amount of flow through the graft. But the pathophysiology of the thrombotic episode is not totally clear and other factors as edema due to ischemia and preservation or pancreatic enzyme damage to vascular endothelium (4), and eventually the pancreas being a low-flow state organ (5), all may play a role.