Increased natural killer cell subsets with inhibitory cytokines and inhibitory surface receptors in patients with recurrent miscarriage and decreased or normal subsets in kidney transplant recipients late post-transplant

Patients with recurrent miscarriage (RM) show up-regulated cytotoxic natural killer (NK) cells that are suspected to play a causal role in abortion. In the present study, we investigated counter-regulating inhibitory mechanisms and compared the results in RM patients with those of healthy controls (HC), patients with end-stage renal disease (ESRD) and kidney transplant recipients late post-transplant (TX). NK, NK T and T cell subsets were analysed in the peripheral blood of 31 RM, 14 female ESRD and nine female TX patients as well as 21 female HC using eight-colour fluorescence flow cytometry. Compared with HC, RM patients showed significantly higher absolute numbers of CD56⁺ NK cells co-expressing the phenotype interferon (IFN)-γR⁺ , IL-4⁺ , transforming growth factor (TGF)-β⁺ , IL-4⁺ human leucocyte antigen D-related (HLA-DR)⁺ , TGF-β⁺ HLA-DR⁺ , IL-4⁺ TGF-β⁺ , IL-4⁺ TGF-β^- , IFN-γ⁺ and/or IL-10^- IFN-γ⁺ (all P ≤ 0·01), more IL-17⁺ CD56^bright (P = 0·028) NK cells and more CD56^dim CD16⁺ NK cells co-expressing IFN-γR, IFN-γ, IL-4 and/or TGF-β (all P ≤ 0·01). When the same cell subsets were analysed in ESRD or TX patients, cytokine-producing NK cell subsets were not significantly different from those of HC. RM patients showed significantly higher absolute numbers of CD158a⁺ , CD158b⁺ , CD158a^- CD158e⁺ (all P < 0·05), NKG2D⁺ NKG2A⁺ , NKG2D ⁺ NKG2A^- , NKG2D⁺ and/or NKG2A⁺ (all P ≤ 0·01) CD56⁺ NK cells and higher CD158a⁺ , CD158b⁺ (all P < 0·05), NKG2D⁺ and/or NKG2A⁺ (all P < 0·01) CD56^dim+ CD16⁺ NK cells than HC. In contrast, ESRD patients had normal and TX recipients had lower CD158a⁺ and NKG2D⁺ NKG2A^- CD56⁺ NK cells and lower CD158a⁺ CD56^dim+ CD16⁺ NK cells (all P < 0·05) than HC. RM patients have abnormally high circulating NK cells expressing inhibitory cytokines and inhibitory surface receptors which might contribute to the pathogenesis of RM.

Association of pre- and early post-transplant serum amino acids and metabolites of amino acids and liver transplant outcome

The aim of the present study was to investigate association of serum amino (AA) acids and metabolites of AAs with post-transplant outcome in liver transplant recipients. Eighty-nine patients with end-stage liver diseases and available pre- and early post-transplant serum were characterised as patients with (GI) and without one-year mortality (GII) and patients with and without early graft dysfunction (EAD). A panel of pre- and early post-transplant serum levels of AAs and early and metabolites of tryptophan were measured using tandem mass spectrometry. Patient groups had significantly higher pre-transplant serum levels of phenylalanine, tryptophan, and tryptophan metabolites than healthy controls (for all p<0.001). Pre-transplant serum levels of all these parameters were significantly higher in GI than in GII (for all p<0.001). GI had a higher MELD score and re-transplantation number than GII (p≤0.005 for both investigations). Serum bilirubin on day 5 and serum phenylalanine on day 10 post-transplant were associated parameters of mortality, whereas day 1post-transplant phenylalanine and kynurenine and female gender were associated parameters of EAD. Our results indicate that pre- and early post-transplant levels of phenylalanine, tryptophan and metabolites of tryptophan are increased in patients and are associated with EAD and one-year mortality in liver transplant recipients.

Association of peripheral NK cell counts with Helios+ IFN-γ- Tregs in patients with good long-term renal allograft function

Little is known about a possible interaction of natural killer (NK) cells with regulatory T cells (T_reg ) in long-term stable kidney transplant recipients. Absolute counts of lymphocyte and T_reg subsets were studied in whole blood samples of 136 long-term stable renal transplant recipients and 52 healthy controls using eight-colour fluorescence flow cytometry. Patients were 1946 ± 2201 days (153-10 268 days) post-transplant and showed a serum creatinine of 1·7 ± 0·7 mg/dl. Renal transplant recipients investigated > 1·5 years post-transplant showed higher total NK cell counts than recipients studied < 1·5 years after transplantation (P = 0·006). High NK cells were associated with high glomerular filtration rate (P = 0·002) and low serum creatinine (P = 0·005). Interestingly, high NK cells were associated with high CD4⁺ CD25⁺ CD127^- forkhead box protein 3 (FoxP3⁺ ) T_reg that co-express the phenotype Helios⁺ interferon (IFN)-γ^- and appear to have stable FoxP3 expression and originate from the thymus. Furthermore, high total NK cells were associated with T_reg that co-express the phenotypes interleukin (IL)-10^- transforming growth factor (TGF)-β⁺ (P = 0·013), CD183⁺ CD62L^- (P = 0·003), CD183⁺ CD62⁺ (P = 0·001), CD183^- CD62L⁺ (P = 0·002), CD252^- CD152⁺ (P < 0·001), CD28⁺ human leucocyte antigen D-related (HLA-DR^- ) (P = 0·002), CD28⁺ HLA-DR⁺ (P < 0·001), CD95⁺ CD178^- (P < 0·001) and CD279^- CD152⁺ (P < 0·001), suggesting that these activated T_reg home in peripheral tissues and suppress effector cells via TGF-β and cytotoxic T lymphocyte-associated protein 4 (CTLA-4). The higher numbers of NK and T_reg cell counts in patients with long-term good allograft function and the statistical association of these two lymphocyte subsets with each other suggest a direct or indirect (via DC) interaction of these cell subpopulations that contributes to good long-term allograft acceptance. Moreover, we speculate that regulatory NK cells are formed late post-transplant that are able to inhibit graft-reactive effector cells.

Characterization of mannose-binding lectin (MBL) variants by allele-specific sequencing of MBL2 and determination of serum MBL protein levels

Mannose-binding lectin (MBL) is a major component of the lectin pathway of complement activation. High and low MBL levels have been associated with susceptibility and severity of a variety of infectious and autoimmune diseases. Several single-nucleotide polymorphisms (SNPs) in the promoter region and exon 1 of the MBL2 gene are responsible for variations in serum MBL levels. We developed a sequence-based typing method for allele-specific MBL2 genotyping and measured serum MBL protein levels in 24 German blood donors. We identified the common MBL2 haplotypes including five promoter polymorphisms in linkage with the Q allele and correlated serum MBL levels with the respective genotypes. The genotyping method presented here could provide a basis for confirmatory studies in larger cohorts.

Ceppellini Lecture 2012: collateral damage from HLA mismatching in kidney transplantation

Inclusion of human leukocyte antigen (HLA) matching in donor kidney allocation schemes has been based solely on its association with graft survival. Other long-term effects associated with HLA incompatibility are largely unexplored. Data from deceased donor kidney transplants reported to the Collaborative Transplant Study have been analyzed to assess the relation between HLA mismatching and clinical events to 3 years post-transplant, and an overview of these analyses is presented. A significant correlation was observed between the number of mismatches and the need for anti-rejection therapy during the first year post-transplant, which was maintained for HLA-DR and HLA-A + B mismatching separately and at years 2 and 3 post-transplant. The number of HLA-DR mismatches and the number of HLA-A + B mismatches as well as rejection treatment showed significant associations with the dose of maintenance steroids. The cumulative incidences of death with a functioning graft from infection or cardiovascular causes, but not from cancer, were also significantly associated with HLA mismatching. The number of HLA-DR mismatches showed a significant association with the incidence of non-Hodgkin lymphoma and hip fractures. These findings show that the adverse consequences of HLA mismatching on kidney transplants extend beyond an effect on graft survival, and include an increased risk of death with a functioning graft, non-Hodgkin lymphoma and hip fracture.

Association between steroid dosage and death with a functioning graft after kidney transplantation

Death with a functioning graft remains a major challenge following kidney transplantation. Steroid dosing may be a modifiable risk factor. Collaborative Transplant Study (CTS) data were analyzed to assess the relationship between long-term steroid dose and death with function during years 2-5 posttransplant in 41 953 adult recipients of a deceased-donor kidney transplant during 1995-2010. Steroid dose at year 1 correlated significantly with death with function overall, and with death due to cardiovascular disease or infection (all p < 0.001). In patients with optimal graft function (serum creatinine <130 µmol/L) and no anti-rejection treatment during (a) year 1 (b) years 1 and 2, these significant associations remained (all p < 0.001). The center-specific incidence of steroid withdrawal during year 2 showed a significant inverse association with death due to cardiovascular disease (p < 0.001) or infection (p < 0.001) overall, and within the subpopulation with good graft function and no rejection during year 1 (p = 0.002 and p < 0.001, respectively). Maintenance steroid dose shows a highly significant association with death with a functioning graft caused by cardiovascular disease or infection during years 2-5 after kidney transplantation, even in patients with good graft outcomes in whom steroid treatment would appear to be unnecessary.

Influence of test technique on sensitization status of patients on the kidney transplant waiting list

The exquisitely sensitive single antigen bead (SAB) technique was shown to detect human leukocyte antigen (HLA) antibodies in sera of healthy male blood donors. Such false reactions can have an impact on critical decisions, especially with respect to the determination of unacceptable HLA-antigen mismatches in patients awaiting a kidney transplant. We tested pretransplant sera of 534 patients on the kidney waiting list using complement-dependent cytotoxicity (CDC), enzyme-linked immunosorbent assay (ELISA) and SAB in parallel. Evidence of HLA antibodies was obtained in 5% of patients using CDC, 14% using ELISA, and 81% using SAB. Among patients without history of an immunizing event, 77% showed evidence of HLA antibodies in SAB. In contrast 98% of these patients were negative in ELISA and CDC. In patients without an immunizing event, SAB-detected antibodies reacted not always weakly but with mean fluorescence intensity (MFI) values as high as 14 440. High-MFI-value antibodies were found in some of these patients with HLA specificities that are rather common in general population, consideration of which would lead to unjustified exclusion of potential kidney donors. False SAB reactions can be unveiled by testing with additional antibody assays. Denial of donor kidneys to recipients based on HLA-antibody specificities detected exclusively in the SAB assay is not advisable.

No impact of KIR-ligand mismatch on allograft outcome in HLA-compatible kidney transplantation

Natural killer (NK) cell function can be modulated by the killer cell immunoglobulin-like receptors (KIR) which interact with human leukocyte antigen (HLA) class I molecules on target cells. KIR-ligand mismatching has recently been shown by van Bergen et al. (American Journal of Transplantation 2011; 11(9): 1959-1964) to be a significant risk factor for long-term graft loss in HLA-A, -B and -DR compatible kidney transplants. To verify this potentially important finding, we performed genotyping of 608 deceased-donor kidney graft recipients and their HLA-A, -B and -DR compatible donors for KIR and HLA, using samples and clinical data provided by the Collaborative Transplant Study. Graft survival of KIR-ligand-matched and -mismatched transplants was compared. We found no impact of KIR-ligand mismatching on 10-year graft survival in HLA-A, -B, -DR compatible kidney transplants. Further analysis did not reveal a significant effect of recipient activating/inhibitory KIR or KIR genotypes on graft survival. Our data do not support the concept that KIR-HLA matching might serve as a tool to improve long-term renal allograft survival.

Recent developments in desensitization of crossmatch-positive kidney transplant recipients

Currently, there are two major options for the successful and timely transplantation of sensitized kidney transplant recipients: (1) avoidance of the sensitization barrier using special allocation programs, or (2) desensitization. In the case of broadly sensitized kidney patients, a combination of both options might be necessary. This review focuses on new advances in desensitization of crossmatch-positive kidney transplant recipients which include immunoadsorption and the administration of new substances such as the complement C5 inhibitor eculizumab. Finally, integrated algorithms that combine different measures are acknowledged.