Preservation of human placenta facilitates multicenter studies on the local immune response in normal and aberrant pregnancies

Our standard procedure for phenotypic and functional analysis of immune cells present in the placenta is to isolate leukocytes from the decidua within five hours of the delivery. However, this results in logistical problems with deliveries at night, weekends or in other medical centers. Collecting placentas after complicated pregnancies is even more difficult owing to the low prevalence and the often unscheduled delivery. The aim was to investigate the possibility of preserving the human placenta before phenotypic and functional analysis of decidual lymphocytes. Placentas were obtained after uncomplicated pregnancy. The tissue was divided into two equal parts: decidual lymphocytes from one part were isolated within five hours according to our standard procedure, whereas the other part was preserved in either Celsior(®), a storage solution for solid organ preservation, or phosphate-buffered saline (PBS) for 24h at 4°C before isolation. Overall, the phenotype and functional capacity of decidual lymphocytes isolated within five hours was comparable to decidual lymphocytes isolated after 24-h preservation in Celsior(®) or PBS. Minor differences were found between decidual lymphocytes isolated within five hours and decidual lymphocytes isolated after 24-h preservation in Celsior(®). The results indicate that PBS is sufficient to preserve the placenta for 24h for phenotypical and functional studies. The ability to preserve the placenta will simplify the procedure for the isolation of decidual lymphocytes and makes it easier to analyze tissue from women who deliver during the night, at weekends or in other hospitals, and possibly even women with complicated pregnancies.

Beneficial or harmful effect of antipaternal human leukocyte antibodies on pregnancy outcome? A systematic review and meta-analysis

PROBLEM

During pregnancy, antibodies are induced that target the paternal human leukocyte antigens of the semi-allogeneic fetus. The level and presence of these antibodies have been reported increased as well as decreased for a variety of pregnancy complications; the clinical relevance and consequences of these antibodies are not very clear. Therefore, the objective of this review is to determine whether the presence of antipaternal antibodies influences pregnancy outcome.

METHOD

We performed a systematic search of studies that described the effect of antipaternal antibodies on pregnancy complications. The primary outcome was the risk ratio for HLA class I and class II antibodies on pregnancy complications. Furthermore, we calculated the risk for first- and third-trimester complications.

RESULTS

The seventeen studies that were selected for meta-analysis showed high level of statistical and clinical heterogeneity. In the meta-analysis, we found no significant effect of HLA class I or class II antibodies on pregnancy outcome.

CONCLUSION

No consistent conclusions can be drawn from the meta-analysis. Discrepancies in the meta-analysis are the result of different screening techniques, varying time points of screening, and use of incorrect control groups. Furthermore, more detailed analyses of the characteristics and specificity of the antibodies involved are essential.

HLA-targeted cell sorting of microchimeric cells opens the way to phenotypical and functional characterization

Microchimerism refers to the presence of less than 1% of non-host cells in a person. Our group developed a reliable method for separating viable microchimeric cells from the host environment. Optimal separation of microchimeric cells at proportions as low as 0.01% could be established with two monoclonal antibodies directed against different HLA antigens, one targeting the microchimeric cells and the other the host cells. Purity of separated cell populations was validated by HLA-allele-specific and Y-chromosome directed real-time qPCR assays. The methodology was used successfully to separate microchimeric maternal cells from child umbilical cord mononuclear cells after pregnancy. Cell sorting with HLA monoclonal antibodies targeting allelic differences enables reliable microchimeric cell detection and separation in blood specimens. With this approach, maximal enrichment of potentially viable microchimeric cells from a background cell population is reached, which opens the way to phenotypical and functional characterization of microchimeric cells.

Autologous bone marrow-derived mesenchymal stromal cells for the treatment of allograft rejection after renal transplantation: results of a phase I study

Despite excellent short-term results, long-term survival of transplanted kidneys has not improved accordingly. Although alloimmune responses and calcineurin inhibitor-related nephrotoxicity have been identified as main drivers of fibrosis, no effective treatment options have emerged. In this perspective, mesenchymal stromal cells (MSCs) are an interesting candidate because of their immunosuppressive and regenerative properties. Of importance, no other clinical studies have investigated their effects in allograft rejection and fibrosis. We performed a safety and feasibility study in kidney allograft recipients to whom two intravenous infusions (1 million cells per kilogram) of autologous bone marrow (BM) MSCs were given, when a protocol renal biopsy at 4 weeks or 6 months showed signs of rejection and/or an increase in interstitial fibrosis/tubular atrophy (IF/TA). Six patients received MSC infusions. Clinical and immune monitoring was performed up to 24 weeks after MSC infusions. MSCs fulfilled the release criteria, infusions were well-tolerated, and no treatment-related serious adverse events were reported. In two recipients with allograft rejection, we had a clinical indication to perform surveillance biopsies and are able to report on the potential effects of MSCs in rejection. Although maintenance immunosuppression remained unaltered, there was a resolution of tubulitis without IF/TA in both patients. Additionally, three patients developed an opportunistic viral infection, and five of the six patients displayed a donor-specific downregulation of the peripheral blood mononuclear cell proliferation assay, not reported in patients without MSC treatment. Autologous BM MSC treatment in transplant recipients with subclinical rejection and IF/TA is clinically feasible and safe, and the findings are suggestive of systemic immunosuppression.

EBV BILF1 evolved to downregulate cell surface display of a wide range of HLA class I molecules through their cytoplasmic tail

Coevolution of herpesviruses and their hosts has driven the development of both host antiviral mechanisms to detect and eliminate infected cells and viral ploys to escape immune surveillance. Among the immune-evasion strategies used by the lymphocryptovirus (γ(1)-herpesvirus) EBV is the downregulation of surface HLA class I expression by the virally encoded G protein-coupled receptor BILF1, thereby impeding presentation of viral Ags and cytotoxic T cell recognition of the infected cell. In this study, we show EBV BILF1 to be expressed early in the viral lytic cycle. BILF1 targets a broad range of HLA class I molecules, including multiple HLA-A and -B types and HLA-E. In contrast, HLA-C was only marginally affected. We advance the mechanistic understanding of the process by showing that the cytoplasmic C-terminal tail of EBV BILF1 is required for reducing surface HLA class I expression. Susceptibility to BILF1-mediated downregulation, in turn, is conferred by specific residues in the intracellular tail of the HLA class I H chain. Finally, we explore the evolution of BILF1 within the lymphocryptovirus genus. Although the homolog of BILF1 encoded by the lymphocryptovirus infecting Old World rhesus primates shares the ability of EBV to downregulate cell surface HLA class I expression, this function is not possessed by New World marmoset lymphocryptovirus BILF1. Therefore, this study furthers our knowledge of the evolution of immunoevasive functions by the lymphocryptovirus genus of herpesviruses.

Novel strategies for immunological monitoring of kidney transplant recipients: from microRNA to alloantibodies

Predicting and diagnosing acute kidney allograft rejection by non-invasive biomarkers is a major goal in clinical transplantation research. Such biomarkers can be reduced to the various stages of the alloimmune response, from transcriptional regulation to immunological effector mechanisms. Here, we describe novel insights into exciting areas of transplantation-related biomarker research that may be translated to non-invasive monitoring strategies. First, we will elaborate on microRNAs, which represent stable, small non-coding ribonucleic acid molecules that can specifically regulate gene expression. Secondly, we will discuss novel methods to monitor human leukocyte antigen (HLA)-specific B cells, as well as the anti-HLA antibodies they produce. Incorporation of these new biomarkers and methodologies into cross-platform biomarker panels may help to improve non-invasive prediction and detection of allograft rejection.

Stimulation of human EBV- and CMV-specific cytolytic effector function using allogeneic HLA molecules

Viral infection is a major cause of morbidity and mortality, and there are few therapeutic options available to augment a virus-specific T cell response. Although allo-HLA cross-reactivity from virus-specific memory T cells is common, it is unclear whether priming with specific allogeneic cells could conversely elicit a viral peptide/self-HLA restricted cytotoxic T cell response in humans. First, we used the previously described allo-HLA-B*44:02 cross-reactivity of EBV peptide/HLA-B8 restricted T cells, to determine whether allogeneic HLA stimulation can elicit a cytolytic immune response against EBV. HLA-B8(+) HLA-B44(-) EBV-seropositive PBMCs were stimulated with either HLA-B*44:02(+) or HLA-B*44:03(+) mismatched irradiated PBMCs in a 7-10 d MLR. The allo-HLA stimulated responder cells were then evaluated for cytotoxicity using EBV peptide loaded autologous target cells and unloaded HLA-B8(+) EBV LCL target cells. PBMCs from EBV-seropositive donors gained EBV-specific cytolytic effector function following specific allo-HLA stimulation. Finally, we also elicited cytolytic CMV-specific responses using specific allogeneic cell stimulation, to confirm that this technique can be used to elicit viral peptide/self-HLA restricted responses even from nonpublic TCR responses. Allogeneic cell stimulation used as a cell therapy may be a potential tool to augment an antiviral T cell response in patients with EBV or CMV infection.

The impact of frequent HLA haplotypes in high linkage disequilibrium on donor search and clinical outcome after unrelated haematopoietic SCT

The MHC region on chromosome 6 contains a large number of non-HLA genes next to the HLA genes. Matching for HLA in unrelated hematopoietic SCT (HSCT) does not necessarily mean that these non-HLA genes are also matched. We selected 348 Northwest European patients transplanted with an HLA-A-, -B-, -C-, -DRB1-, -DQB1-matched unrelated donor (MUD) between 1987 and 2008. Patients' haplotypes were identified via descend. We were unable to determine the haplotypes of the donor; therefore we used frequent haplotypes (FH) in high linkage disequilibrium (LD) as a proxy for haplotype matching. Presence of a FH in a patient positively affected the probability and speed of identifying a matched unrelated donor. Competing risk survival analysis showed that patients with one or two FH have a statistically significantly decreased probability of developing ≥ grade II acute GVDH (aGVHD) without increased risk of relapse compared to patients without FH (HR (95% CI): 0.53 (0.31-0.91)). This association was strongest for those FH with the highest LD between both HLA-A and -C or -B, and HLA-C or -B and -DRB1 (HR (95% CI): 0.49 (0.26-0.92)). These results extend evidence that non-HLA allele coding regions have a significant impact on development of ≥ grade II aGVHD. We conclude that there is more to successful HSCT than matching for HLA genes.

Immune responses against islet allografts during tapering of immunosuppression--a pilot study in 5 subjects

Transplantation of isolated islet of Langerhans cells has great potential as a cure for type 1 diabetes but continuous immune suppressive therapy often causes considerable side effects. Tapering of immunosuppression in successfully transplanted patients would lower patients' health risk. To identify immune biomarkers that may prove informative in monitoring tapering, we studied the effect of tapering on islet auto- and alloimmune reactivity in a pilot study in five transplant recipients in vitro. Cytokine responses to the graft were measured using Luminex technology. Avidity of alloreactive cytotoxic T Lymphocytes (CTL) was determined by CD8 blockade. The influence of immunosuppression was mimicked by in vitro replenishment of tacrolimus and MPA, the active metabolite of mycophenolate mofetil. Tapering of tacrolimus was generally followed by decreased C-peptide production. T-cell autoreactivity increased in four out of five patients during tapering. Overall alloreactive CTL precursor frequencies did not change, but their avidity to donor mismatches increased significantly after tapering (P = 0·035). In vitro addition of tacrolimus but not MPA strongly inhibited CTL alloreactivity during tapering and led to a significant shift to anti-inflammatory graft-specific cytokine production. Tapering of immunosuppression is characterized by diverse immune profiles that appear to relate inversely to plasma C-peptide levels. Highly avid allospecific CTLs that are known to associate with rejection increased during tapering, but could be countered by restoring immune suppression in vitro. Immune monitoring studies may help guiding tapering of immunosuppression after islet cell transplantation, even though we do not have formal prove yet that the observed changes reflect direct effects of immune suppression on immunity.

The functional polymorphism Ala258Ser in the innate receptor gene ficolin-2 in the donor predicts improved renal transplant outcome

BACKGROUND

Innate immunity plays a role in controlling adaptive immune responses.

METHODS

We investigated the clinical relevance of single nucleotide polymorphisms in 22 genes encoding innate, secreted, and signaling pattern recognition receptors in a total of 520 donor-recipient pairs of postmortem, human leukocyte antigen-DR-compatible kidney transplantations. Associations with rejection incidence were tested in an a priori randomized training set and validation set.

RESULTS

Polymorphisms in TLR-3 (rs3775296) in the recipients and in ficolin-2 (rs7851696; Ala258Ser) and C1qR1 (rs7492) in the donors showed the strongest association with severe rejection. In multivariate analysis, presence of the ficolin-2 Ala258Ser variant in the donor predicted lower incidence of severe rejection (odds ratio=0.3; 95% confidence interval, 0.1-0.9; P=0.024) and of graft loss (hazard ratio=0.5; 95% confidence interval, 0.2-1.0; P=0.046) independently of clinical risk factors. Ficolin-2 messenger RNA expression was detected in pretransplantation biopsies from 69 donor grafts. Serum and tissue ficolin-2 levels were unaffected by genotype. Ficolin-2 protein, which bound to dying cells, was detected in donor kidneys in a passenger leukocyte-like pattern. Indeed, monocytes, monocyte-derived macrophages, and peripheral blood mononuclear cells expressed ficolin-2. Donor grafts with the ficolin-2 Ala258Ser variant contained significantly elevated expression of interleukin 6, having ascribed cytoprotective effects. It has been described that Ala258Ser leads to increased binding capacity of ficolin-2 to N-acetylglucosamine.

CONCLUSIONS

Presence of the ficolin-2 Ala258Ser polymorphism in the donor independently predicts improved graft outcome. Based on mechanistic data, we propose that this functional polymorphism leads to more efficient handling of injured cells by phagocytozing cells, resulting in decreased intragraft exposure to danger signals and dampened alloimmune responses.

Genetic HLA associations in complex regional pain syndrome with and without dystonia

We previously showed evidence for a genetic association of the human leukocyte antigen (HLA) system and complex regional pain syndrome (CRPS) with dystonia. Involvement of the HLA system suggests that CRPS has a genetic component with perturbed regulation of inflammation and neuroplasticity as possible disease mechanisms. However, it is at present unclear whether the observed association with HLA-B62 and HLA-DQ8 in CRPS patients with dystonia also holds true for patients without dystonia. Therefore, we tested the possible association with HLA-B62 and HLA-DQ8 in a clinically homogeneous group of 131 CRPS patients without dystonia. In addition, we investigated the possible association with other alleles of the HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ loci. We showed an increased prevalence of HLA-DQ8 (molecularly typed as HLA-DQB1*03:02; OR = 1.65 [95% CI 1.12-2.42], P = .014) in CRPS without dystonia, whereas no association was observed for HLA-B62 (molecularly typed as HLA-B*15:01; OR = 1.22 [95% CI .78-1.92], P = .458). Our data suggest that CRPS with and CRPS without dystonia may be genetically different, but overlapping, disease entities because only HLA-DQ8 is associated with both. The findings also indicate that distinct biological pathways may play a role in both CRPS subtypes.

PERSPECTIVE

This study is the first to replicate a specific HLA region conferring genetic risk for the development of CRPS. Moreover, associations of HLA-DQ8 with both CRPS with and CRPS without dystonia, and HLA-B62 only with CRPS with dystonia, suggest that these disease entities may be genetically different, but overlapping.

The risk of cancer is not increased in patients with multiple kidney transplantations

BACKGROUND

The aim of this study was to investigate whether the number of transplantations, as a marker of the graft rejection status of the patient, is associated with an increased risk of malignancies.

METHODS

In a cohort study, 1213 patients, receiving a kidney transplantation between 1966 and 1995 at the Leiden University Medical Center, were analyzed. All cutaneous squamous cell carcinoma and internal malignancies, which had developed between 1966 and 2007, were recorded. The influence of number of transplantations, age, sex and time on immunosuppression on the risk of squamous cell carcinoma and internal malignancies was investigated by time-dependent multivariate Cox's proportional hazard models.

RESULTS

Of the 1213 kidney transplant recipients, 319 received a second kidney, 78 a third; 13 of them a fourth and 4 of them a fifth transplantation. After adjustment for potentially confounding factors, including age, sex and years on immunosuppressive therapy we did not detect an increased risk of cancer in patients with multiple transplantations. On the contrary, patients with three or more transplantations had a 1.6-fold decreased risk of squamous cell carcinomas and a 3.6-fold decreased risk of internal malignancies.

CONCLUSION

We conclude that kidney transplant recipients with three or more transplantations do not have an increased risk of cutaneous squamous cell carcinoma and internal malignancies.

A NOVel ELISPOT assay to quantify HLA-specific B cells in HLA-immunized individuals

Quantification of the humoral alloimmune response is generally achieved by measuring serum HLA antibodies, which provides no information about the cells involved in the humoral immune response. Therefore, we have developed an HLA-specific B-cell ELISPOT assay allowing for quantification of B cells producing HLA antibodies. We used recombinant HLA monomers as target in the ELISPOT assay. Validation was performed with human B-cell hybridomas producing HLA antibodies. Subsequently, we quantified B cells producing HLA antibodies in HLA-immunized individuals, non-HLA-immunized individuals and transplant patients with serum HLA antibodies. B-cell hybridomas exclusively formed spots against HLA molecules of corresponding specificity with the sensitivity similar to that found in total IgG ELISPOT assays. HLA-immunized healthy individuals showed up to 182 HLA-specific B cells per million total B cells while nonimmunized individuals had none. Patients who were immunized by an HLA-A2-mismatched graft had up to 143 HLA-A2-specific B cells per million total B cells. In conclusion, we have developed and validated a highly specific and sensitive HLA-specific B-cell ELISPOT assay, which needs further validation in a larger series of transplant patients. This technique constitutes a new tool for quantifying humoral immune responses.

Strategies to work with HLA data in human populations for histocompatibility, clinical transplantation, epidemiology and population genetics: HLA-NET methodological recommendations

HLA-NET (a European COST Action) aims at networking researchers working in bone marrow transplantation, epidemiology and population genetics to improve the molecular characterization of the HLA genetic diversity of human populations, with an expected strong impact on both public health and fundamental research. Such improvements involve finding consensual strategies to characterize human populations and samples and report HLA molecular typings and ambiguities; proposing user-friendly access to databases and computer tools and defining minimal requirements related to ethical aspects. The overall outcome is the provision of population genetic characterizations and comparisons in a standard way by all interested laboratories. This article reports the recommendations of four working groups (WG1-4) of the HLA-NET network at the mid-term of its activities. WG1 (Population definitions and sampling strategies for population genetics’ analyses) recommends avoiding outdated racial classifications and population names (e.g. ‘Caucasian’) and using instead geographic and/or cultural (e.g. linguistic) criteria to describe human populations (e.g. ‘pan-European’). A standard ‘HLA-NET POPULATION DATA QUESTIONNAIRE’ has been finalized and is available for the whole HLA community. WG2 (HLA typing standards for population genetics analyses) recommends retaining maximal information when reporting HLA typing results. Rather than using the National Marrow Donor Program coding system, all ambiguities should be provided by listing all allele pairs required to explain each genotype, according to the formats proposed in ‘HLA-NET GUIDELINES FOR REPORTING HLA TYPINGS’. The group also suggests taking into account a preliminary list of alleles defined by polymorphisms outside the peptide-binding sites that may affect population genetic statistics because of significant frequencies. WG3 (Bioinformatic strategies for HLA population data storage and analysis) recommends the use of programs capable of dealing with ambiguous data, such as the ‘gene[rate]’ computer tools to estimate frequencies, test for Hardy–Weinberg equilibrium and selective neutrality on data containing any number and kind of ambiguities. WG4 (Ethical issues) proposes to adopt thorough general principles for any HLA population study to ensure that it conforms to (inter)national legislation or recommendations/guidelines. All HLA-NET guidelines and tools are available through its website http://hla-net.eu.

Structural aspects of human leukocyte antigen class I epitopes detected by human monoclonal antibodies

This study addresses the concept that human leukocyte antigen (HLA) class I-specific alloantibodies are specific for epitopes that correspond to HLAMatchmaker-defined eplets. Eplets are essential parts of so-called structural epitopes that make contact with the 6 complementarity determining regions of an antibody. From published molecular models of crystallized protein antigen-antibody complexes, we have calculated that contact residues on structural HLA epitopes should reside within a 15-Å radius of a mismatched eplet. This study addresses the structural basis of high-frequency HLA class I epitopes reacting with human monoclonal antibodies (mAbs) derived from women sensitized during pregnancy. All mAbs were tested in Luminex assays with single HLA allele panels. The HLAMatchmaker algorithm was used to determine their specificity in context with eplet sharing between the immunizing allele and antibody-reactive alleles. To assess the autoreactive B cell origin of these antibodies, we have applied the recently developed nonself-self paradigm of epitope immunogenicity to analyze residue differences between the immunizer and the alleles of the antibody producer. A total of 9 mAbs were specific for epitopes associated with the 41T, 80NRG, 163LW, 69AA, or 80ERILR eplets. In each case, the immunizing allele had within 15 Å of the mismatched eplet, no residue differences with 1 of the alleles of the antibody producer. This observation is consistent with the concept that these mAbs originated from B cells with self HLA immunoglobulin receptors. Eplet-carrying alleles exhibited different levels of reactivity, which, when compared with the immunizing allele, ranged from high to intermediate to very low. In many cases, lower reactivities were associated with differences from self to nonself residues in surface locations within 15 Å of the specific eplet. Apparently, such locations may serve as critical contact sites for the antibody. In other cases, other residue differences did not appear to affect binding with the antibody, suggesting that these locations do not play a major role in antibody binding. For these mAbs we did not obtain convincing evidence that residue differences in hidden positions below the molecular surface had significant effects on antibody binding. These findings have increased our understanding of the structural basis of the immunogenicity and antigenicity of HLA class I epitopes and provide a basis for interpreting HLA antibody reactivity patterns in Luminex assays with single alleles.

TCR cross-reactivity and allorecognition: new insights into the immunogenetics of allorecognition

Alloreactive T cells are core mediators of graft rejection and are a potent barrier to transplantation tolerance. It was previously unclear how T cells educated in the recipient thymus could recognize allogeneic HLA molecules. Recently it was shown that both naïve and memory CD4+ and CD8+ T cells are frequently cross-reactive against allogeneic HLA molecules and that this allorecognition exhibits exquisite peptide and HLA specificity and is dependent on both public and private specificities of the T cell receptor. In this review we highlight new insights gained into the immunogenetics of allorecognition, with particular emphasis on how viral infection and vaccination may specifically activate allo-HLA reactive T cells. We also briefly discuss the potential for virus-specific T cell infusions to produce GvHD. The progress made in understanding the molecular basis of allograft rejection will hopefully be translated into improved allograft function and/or survival, and eventually tolerance induction.

KIR-ligand mismatches are associated with reduced long-term graft survival in HLA-compatible kidney transplantation

Natural killer (NK) cells are cytotoxic lymphocytes of the innate immune system with the ability to detect HLA class I disparities via killer-cell immunoglobulin-like receptors (KIR). To test whether such KIR-ligand mismatches contribute to the rejection of human solid allografts, we did a retrospective cohort study of 397 HLA-DR-compatible kidney transplantations and determined the KIR and HLA genotypes of recipients and the HLA genotypes of donors. In transplantations compatible for HLA-A, HLA-B and HLA-DR (n = 137), in which a role for T cells and HLA antibodies in rejection was minimized, KIR-ligand mismatches were associated with an approximately 25% reduction in 10-year death-censored graft survival (p = 0.043). This effect was comparable to the effect of classical HLA-A and HLA-B incompatibility, and in HLA-A,-B-incompatible transplantations (n = 260) no significant additional effect of KIR-ligand mismatches was observed. Multivariate Cox regression analysis confirmed the effect of KIR-ligand mismatching as an independent risk factor in HLA-A,-B,-DR-compatible transplantations (hazard ratio 2.29, range 1.03-5.10, p = 0.043). This finding constitutes the first indication that alloreactive NK cells may thwart the success of HLA-compatible kidney transplantations, and suggests that suppression of NK-cell activity can improve the survival of such kidney grafts.

Changes in cytokine production and composition of peripheral blood leukocytes during pregnancy are not associated with a difference in the proliferative immune response to the fetus

We analyzed peripheral blood from women at term pregnancy for leukocyte composition, in vitro proliferative responses and cytokine production after nonspecific and fetus-specific stimulation. Maternal peripheral blood mononuclear cells (PBMCs) were collected and stimulated with umbilical cord blood (UCB) of the mother's own child, third-party UCB, nonspecific stimulus phytohemagglutinin, and anti-CD3 antibody, with PBMCs of nonpregnant women (cPBMC) as controls. Nine combinations of patient, child, third party child, and controls were selected on basis of sharing one human leukocyte antigen (HLA)-DR antigen. The response of mPBMC upon specific stimulation with fetal antigens was similar to that of cPBMC. No differences were found when comparing the mother's response upon stimulation to her own child with stimulation to that with a control child. Nonspecific stimulation with phytohemagglutinin and anti-CD3 antibody did not reveal a difference in proliferation rate between mPBMC and cPBMC. However, mPBMC contained a higher percentage of CD14(+) cells (p = 0.001) and activated T cells (CD25(dim), p < 0.0001), but a lower percentage CD16(-)CD56(bright) natural killer (NK) cells (p = 0.001) and CD16(+)CD56(+) NK cells (p = 0.003). mPBMC produced more interleukin (IL)-6, IL-10, and IL-17 compared with cPBMC (p < 0.05). We found differences in lymphocyte composition and cytokine production between mPBMC and cPBMC. These differences did not result in quantitative changes in proliferative responses during pregnancy compared with responses in nonpregnant controls.

C4d staining in renal allograft biopsies with early acute rejection and subsequent clinical outcome

BACKGROUND AND OBJECTIVES

Diffuse C4d staining in peritubular capillaries (PTCs) during an acute rejection episode (ARE) is the footprint of antibody-mediated rejection. In current clinical practice, diffuse C4d+ staining during acute rejection is regarded as an inferior prognostic sign. This case-control study investigated the prognostic role of mere C4d staining for graft outcome during an ARE in a well defined cohort of similarly ARE-treated patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

All kidney transplant recipients in the authors' center from January 1, 1995 to December 31, 2005 were reviewed. From these patients, 151 had a clinical ARE. Paraffin and/or frozen material was available for 128 patients showing a histologically proven ARE within the first 6 months after transplantation. All ARE patients were treated similarly with high-dose pulse steroids and in the case of steroid unresponsiveness with anti-thymocyte globulin. Biopsies were scored according to Banff criteria. Frozen and paraffin sections were stained by immunofluorescence (IF) and immunohistochemistry (IHC) for C4d, respectively, and scored for PTC positivity.

RESULTS

Diffuse C4d+ staining in PTCs was found in 12.5% and 4.2% sections stained by IF or by IHC, respectively. Four patients showed diffuse positive staining with both methods but showed no different risk profile from other patients. No relation between C4d staining and clinical parameters at baseline was found. C4d staining was not associated with steroid responsiveness, graft, or patient survival.

CONCLUSIONS

This study shows that C4d staining is not related to clinical outcome in this cohort of histologically proven early AREs.

Eight years of outcomes of the Dutch Living Donor Kidney Exchange Program

In January 2004, the Dutch transplant centers agreed on a protocol for a national Living Donor Kidney Exchange Program for ABO blood type incompatible and positive cross match donor-recipient pairs. Here, we report the results of that program. All transplants performed within the Living Donor Kidney Exchange Program between January 2004 and December 2011 were analysed. We collected demographic data of recipients and donors. Univariate and multivariate Cox proportional hazard analyses were performed, including recipient age, donor age, and reason for participation in the exchange program. We studied overall uncensored survival and graft survival censored for death in both ABO blood type incompatible and positive cross match groups. We enrolled 472 donor-recipient combinations, consisting of 269 ABO blood type incompatible pairs and 203 positive cross match pairs. In the end, we performed 187 kidney transplants (40% of those enrolled) with 83 ABO blood type incompatible and 104 positive cross match pairs. Most of the transplanted recipients (119/187, 64%) had an age difference of less than 5 years with their original incompatible donors. The age differences with their actual donors varied widely, but the number of recipients with a donor > 5 years older was comparable to the number of recipients with a donor > 5 years younger. In the multivariate Cox analysis, age as a continuous variable was found to have a significant influence on graft failure. Nevertheless, the 5-year uncensored survival (85%) and the graft survival censored for death (89%) were excellent and comparable to the results of direct living donation. No differences were found between the ABO incompatible and the positive cross match groups. The Dutch Living Donor Kidney Exchange Program has a high transplant rate of 40%, with excellent 5 year graft survival.