Immunogenetics & transplantation

Willingness of the United States general public to participate in kidney paired donation

2012-03-09T13:49:00.001+01:00

Availability of kidney paired donation (KPD) is increasing in the United States, and a national system through UNOS is forthcoming. However, little is known about attitudes toward KPD among the general public, from which donors (particularly non-directed) are drawn. In a national study, we assessed the public's attitudes regarding participation in KPD. Among 845 randomly selected participants, 85.2% of respondents were either “extremely willing” or “very willing” to participate in KPD. Experiences with the medical or organ transplant systems, such as undergoing surgery, having a primary medical provider, a living will, a friend who donated or received an organ, and considering donation after death, were associated with increased willingness. However, increased age, male sex, African American race, Hispanic ethnicity, distrust of the medical system, and not understanding organ allocation were associated with less willingness. We identify strong support for KPD but some important potential barriers to participation which should be considered as KPD programs are implemented (read more).

Pretransplant Donor-Specific HLA Class-I and -II Antibodies Are Associated with an Increased Risk for Kidney Graft Failure

2012-03-09T13:48:00.001+01:00

Pretransplant risk assessment of graft failure is important for donor selection and choice of immunosuppressive treatment. We examined the relation between kidney graft failure and presence of IgG donor specific HLA antibodies (DSA) or C1q-fixing DSA, detected by single antigen bead array (SAB) in pretransplant sera from 837 transplantations. IgG-DSA were found in 290 (35%) sera, whereas only 30 (4%) sera had C1q-fixing DSA. Patients with both class-I plus -II DSA had a 10 yr graft survival of 30% versus 72% in patients without HLA antibodies (p < 0.001). No significant difference was observed in graft survival between patients with or without C1q-fixing DSA. Direct comparison of both assays showed that high mean fluorescence intensity values on the pan-IgG SAB assay are generally related to C1q-fixation. We conclude that the presence of class-I plus -II IgG DSA as detected by SAB in pretransplant sera of crossmatch negative kidney recipients is indicative for an increased risk for graft failure, whereas the clinical significance of C1q-fixing IgG-DSA could not be assessed due to their low prevalence (read more).

A Novel ELISPOT Assay to Quantify HLA-Specific B Cells in HLA-Immunized Individuals

2012-03-06T21:29:00.000+01:00

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 (read more).

Very Early Recurrence of Anti-Phospholipase A2 Receptor-Positive Membranous Nephropathy After Transplantation

2012-03-06T21:19:00.000+01:00

Membranous nephropathy is a common cause of adult nephrotic syndrome, with recent evidence suggesting that 70% of idiopathic disease is associated with anti-Phospholipase A₂ receptor autoantibodies. We describe a 63-year-old man with membranous nephropathy who underwent a kidney transplant and developed recurrent membranous nephropathy with fine granular co-localization of Phospholipase A₂ receptor and IgG evident on transplant biopsy on day 6 and elevated circulating levels of serum anti-Phospholipase A₂ receptor autoantibody that declined over time in conjunction with improvement in the serum creatinine and urinary protein. This is a very early case of Phospholipase A₂ receptor-associated recurrent membranous nephropathy with circulating anti-Phospholipase A₂ receptor autoantibody, which supports the emerging evidence that idiopathic membranous nephropathy is an autoimmune disease (read more).

ABO-Incompatible Kidney Transplantation Enabled by Non-Antigen-Specific Immunoadsorption.

2012-03-05T19:22:00.000+01:00

BACKGROUND: ABO-incompatible kidney transplantation performed after desensitization with antigen-specific immunoadsorption (IA) results in good outcomes. However, a unique single-use IA device is required, which creates high costs. METHODS: From August 2005 to August 2010, 19 patients were desensitized for ABO-incompatible living donor kidney transplantation. Six patients treated with a single-use antigen-specific IA device and 12 patients treated with a reusable non-antigen-specific IA device were analyzed. RESULTS: Six patients who received antigen-specific IA had a median of 5 IA treatments and 12 patients with non-antigen-specific IA had a median of 6 IA treatments preoperatively. Median average titer drop in Coombs technique was 1.2 in antigen-specific IA and 1.7 in non-antigen-specific IA. In two patients with antigen-specific IA and four patients with non-antigen-specific IA, additional plasmapheresis treatments were necessary for recipient desensitization. Despite six treatments with antigen-specific IA and 12 plasmapheresis treatments, one patient with a starting isoagglutinin titer of 1:1024 (Coombs) could not be transplanted. The 18-month graft survival rate for the 17 ABO-incompatible living donor kidney transplants was 100%. One male recipient who was desensitized with antigen-specific IA died 44 months after transplantation from sudden cardiac death with a serum creatinine of 1.2 mg/dL. At last follow-up, a median of 13 months after transplantation, median serum creatinine for 16 patients was 1.5 mg/dL, median glomerular filtration rate as estimated by the modification of diet in renal disease formula 54 mL/min/1.73 m, and median urinary protein-to-creatinine ratio 0.1, with no differences between treatments. CONCLUSIONS: A reusable non-antigen-specific IA device allows high number of treatments at reasonable cost, and at the same time might deplete human leukocyte antigen-alloantibodies (read more)

MHC Class II Tetramers [BRIEF REVIEWS]

2012-03-03T12:12:00.000+01:00

MHC class II tetramers have emerged as an important tool for characterization of the specificity and phenotype of CD4 T cell immune responses, useful in a large variety of disease and vaccine studies. Issues of specific T cell frequency, biodistribution, and avidity, coupled with the large genetic diversity of potential class II restriction elements, require targeted experimental design. Translational opportunities for immune disease monitoring are driving the rapid development of HLA class II tetramer use in clinical applications, together with innovations in tetramer production and epitope discovery (read more).

A pilot programme of organ donation after cardiac death in China

2012-03-02T08:38:00.000+01:00

China's aims are to develop an ethical and sustainable organ transplantation system for the Chinese people and to be accepted as a responsible member of the international transplantation community. In 2007, China implemented the Regulation on Human Organ Transplantation, which was the first step towards the establishment of a voluntary organ donation system. Although progress has been made, several ethical and legal issues associated with transplantation in China remain, including the use of organs from executed prisoners, organ scarcity, the illegal organ trade, and transplantation tourism (read more).

Clinical relevance of HLA donor-specific antibodies detected by single antigen assay in kidney transplantation

2012-03-01T21:25:00.000+01:00

Clinical relevance of donor-specific antibodies (DSAs) detected by a single antigen Luminex virtual crossmatch in pre-transplant serum samples from patients with a negative cytotoxicity-dependent complement crossmatch is controversial. The aim of this study was to analyse the influence of a pre-transplant positive virtual crossmatch in the outcome of kidney transplantation. Methods. A total of 892 patients who received a graft from deceased donors after a negative cytotoxicity crossmatch were included. Presence of anti-human leucocyte antigen (HLA) antibodies was investigated using a Luminex screening assay and anti-HLA specificities were assigned performing a Luminex single antigen assay. Results. Graft survival was significantly worse among patients with anti-HLA DSA compared to both patients with anti-HLA with no DSA (P = 0.001) and patients without HLA antibodies (P < 0.001) using a log-rank test. No graft survival differences between anti-HLA with no DSA and no HLA antibodies patient groups were observed (P = 0.595). Influence of both anti-Class I and anti-Class II DSA was detected (P < 0.0001 in both cases). When the fluorescence values were stratified in four groups, no significant differences in graft survival were observed among the groups with fluorescence levels >1500 (global P < 0.05). Conclusions. The presence of preformed HLA DSA in transplanted patients with a negative cytotoxicity crossmatch is associated with a lower allograft survival. The detection of anti-HLA with no DSA has no influence in the graft outcome. Finally, there were no demonstrable effects of mean fluorescence intensity (MFI) values > 1500 on graft survival (read more).

Living donor kidney transplantation in crossmatch-positive patients enabled by peritransplant immunoadsorption and anti-CD20 therapy

2012-02-29T08:06:00.002+01:00

Living donor kidney transplantation in crossmatch-positive patients is a challenge that requires specific measures. Ten patients with positive crossmatch results (n = 9) or negative crossmatch results but strong donor-specific antibodies (DSA; n = 1) were desensitized using immunoadsorption (IA) and anti-CD20 antibody induction. IA was continued after transplantation and accompanied by HLA antibody monitoring and protocol biopsies. After a median of 10 IA treatments, all patients were desensitized successfully and transplanted. Median levels of mean fluorescence intensity (MFI) of Luminex-DSA before desensitization were 6203 and decreased after desensitization and immediately before transplantation to 891. Patients received a median of seven post-transplant IA treatments. At last visit, after a median follow-up of 19 months, 9 of 10 patients had a functioning allograft and a median Luminex-DSA of 149 MFI; serum creatinine was 1.6 mg/dl, and protein to creatinine ratio 0.1. Reversible acute antibody-mediated rejection was diagnosed in three patients. One allograft was lost after the second post-transplant year in a patient with catastrophic antiphospholipid syndrome. We describe a treatment algorithm for desensitization of living donor kidney transplant recipients that allows the rapid elimination of DSA with a low rate of side effects and results in good graft outcome (read more).

A rapid diagnostic test for human regulatory T-cell function to enable regulatory T-cell therapy

2012-02-25T09:15:00.000+01:00

Regulatory T cells (CD4⁺CD25^hiCD127^loFOXP3⁺ T cells [Tregs]) are a population of lymphocytes involved in the maintenance of self-tolerance. Abnormalities in function or number of Tregs are a feature of autoimmune diseases in humans. The ability to expand functional Tregs ex vivo makes them ideal candidates for autologous cell therapy to treat human autoimmune diseases and to induce tolerance to transplants. Current tests of Treg function typically take up to 120 hours, a kinetic disadvantage as clinical trials of Tregs will be critically dependent on the availability of rapid diagnostic tests before infusion into humans. Here we evaluate a 7-hour flow cytometric assay for assessing Treg function, using suppression of the activation markers CD69 and CD154 on responder T cells (CD4⁺CD25^– [Tresp]), compared with traditional assays involving inhibition of CFSE dilution and cytokine production. In both freshly isolated and ex vivo expanded Tregs, we describe excellent correlation with gold standard suppressor cell assays. We propose that the kinetic advantage of the new assay may place it as the preferred rapid diagnostic test for the evaluation of Treg function in forthcoming clinical trials of cell therapy, enabling the translation of the large body of preclinical data into potentially useful treatments for human diseases (read more).

Antigen-specific regulatory T cells can induce tolerance to immunogenic grafts without the need for chronic immunosuppression

2012-02-25T09:12:00.000+01:00

Regulatory CD4⁺CD25⁺Foxp3⁺ T cells (Tregs) play an important role in the induction of allospecific tolerance. However tolerance in solid organ transplantation by mere transfer of Tregs has been difficult. Besides this the stability of the differentiation phenotype of Tregs has recently been questioned.

We therefore aimed in generating large numbers of stable allospecific Tregs from naïve T cells by retroviral transduction with Foxp3. These were tested in an immunogenic skin transplantation model (C57BL/6→BALB/c).

We established a system of transduction of mouse T cells with ecotropic retroviruses expressing Foxp3 and Thy1.1 as a surface marker to follow up transduced T cells. Alloantigen-specific Tregs were generated by stimulating naïve recipient CD4⁺ T cells with irradiated donor splenocytes. CD25⁺ and/or CD69⁺ allospecific recipient CD4⁺ T cells were isolated and transduced with Foxp3. Alloantigen-specific Foxp3 T cells (iTregs) showed high expression for the Treg markers Foxp3, CTLA4 and GITR. They could suppress a MLR in an alloantigen-specific manner. Furthermore, they could be expanded up to 18 fold in vitro while maintaining their Treg phenotype and expression of lymph node homing markers like CCR7 and CD62L. iTregs prevented skin graft rejection without the need for chronic immunosuppression and recipients showed systemic allospecific allotolerance. Alloantigen-specific Tregs were far more potent than polyspecific Tregs. Mechanisms of tolerance were graft specific homing, expansion and long-term persistence of Tregs within the graft (>100 days, 90% of intragraft Tregs were alloantigen-specific). In fact, tolerance could be transferred with re-transplantation of the tolerant graft onto secondary recipients. Third party grafts were readily rejected demonstrating specificity of tolerance. Due to the Foxp3 transduction, iTregs did not lose their Treg phenotype.

The results prove that large numbers of stable alloantigen-specific Tregs can be generated from a polyclonal repertoire of naïve T cells. This is the first time that allotolerance was achieved in a non-lymphopenic transplant model using skin grafts in an immunogenic strain combination. Therefore, antigen-specific Tregs might have a huge therapeutic potential after solid organ transplantation (read more).

Effects of Antibody Induction on Transplant Outcomes in Human Leukocyte Antigen Zero-Mismatch Deceased Donor Kidney Recipients

2012-02-25T09:08:00.000+01:00

Background. We aimed to investigate the impact of antibody induction on outcomes in human leukocyte antigen (HLA) 0-mismatched deceased donor kidney recipients.
Methods. Using the Organ Procurement and Transplant Network/United Network of Organ Sharing database as of November 2009, we identified 44,008 adult deceased donor kidney recipients who received primary kidney transplants alone between 2003 and 2008 (HLA 0 mismatch, n=6274; ≥1 mismatch, n=37,734; median follow-up: 834 days). The impact of induction (thymoglobulin, interleukin-2 receptor antagonists [IL-2RA], or alemtuzumab; vs. no induction) on rejection (initial hospitalization, 6 months, first year), death-censored graft failure, and mortality were analyzed using multivariate logistic and Cox regression in the two groups. The impact of individual agents on outcomes was further analyzed in 0-mismatch recipients.
Results. There was a decreased risk of rejection over the first 6 months for HLA 0-mismatch recipients of antibody induction (adjusted odds ratio=0.71, P=0.003), but this effect was not observed at 1 year; in comparison, induction was associated with a reduced risk of rejection over the first year for HLA-mismatched recipients (0.87, P<0.001). The use of thymoglobulin (0.72, P=0.02) and IL-2RA (0.67, P=0.004) was associated with a decreased risk of rejection compared with no-induction at 6 months but was not different at 1 year (thymoglobulin: 0.77, P=0.05; IL-2RA:0.81, P=0.11) in HLA 0-mismatched recipients. Induction was not associated with improved graft or patient survival in HLA 0-mismatch recipients.
Conclusion. In HLA 0-mismatch deceased donor recipients, antibody induction was associated with a decreased risk of rejection at 6 months posttransplant. Its use did not improve graft and patient survival over the follow-up period (read more)

Oxygenated Kidney Preservation Techniques

2012-02-25T09:04:00.000+01:00

Improving preservation techniques to minimize injury is of particular importance in organs from marginal donors. Since the introduction of transplantation and routine use of hypothermic temperatures for kidney preservation, there has been much debate on whether it is necessary to add oxygen to support the low level of metabolism under these conditions. Supplementing the kidney with oxygen during hypothermic preservation is not common practice. However, there is evidence to support its application. Oxygen can be added by various techniques such as retrograde persufflation whereby filtered and humidified oxygen is bubbled through the vasculature; under hyperbaric conditions using specialized pressurized chambers; during hypothermic machine perfusion; with the addition of oxygen carriers; and under normothermic conditions. Evidence suggests that oxygenation is particularly beneficial in restoring cellular levels of adenosine triphosphate after kidneys have been subjected to warm or cold ischemic injury. However, under normal conditions, the benefits are less convincing, but the evidence is insufficient to draw any conclusions. This overview explores the ways in which oxygen can be administered during preservation in experimental and clinical models of kidney transplantation (read more).

Machine Perfusion or Cold Storage in Deceased-Donor Kidney Transplantation

2012-02-23T11:19:00.000+01:00

3-year follow-up shows that machine perfusion (as compared to cold-storage preservation) reduces delayed graft function in kidney donated after either brain death or circulatory death, but it improves graft survival only of kidneys donated after brain death, especially in kidneys recovered from expanded-criteria donors (read more : FREE full text access)

Very long-term follow-up of living kidney donors

2012-02-23T09:30:00.000+01:00

Knowledge of the very long-term consequences of kidney donors has not been previously reported extensively. The 398 persons who had donated a kidney between 1952 and 2008 at Necker hospital were contacted. Among the 310 donors who were located, the survival probabilities for this population were similar to those of the general population and end stage renal disease incidence was 581 per million population per year. All located donors still alive were asked to complete a medico-psychosocial questionnaire and give samples for serum creatinine and urinary albumin assays. Among the 204 donors who responded to the questionnaire, mean eGFR was 64.4 ± 14.6 ml/min per 1.73 m² and mean microalbuminuria was 27.0 ± 83 mg/g. Most donors never regretted the donation and consider that it has no impact on their professional or social lives. Among the 59 donors who gave a kidney more than 30 years ago (mean 40.2 years, range 30–48 years) had a mean eGFR of 67.5 ± 17.4 μmol/l, a mean microalbuminuria level of 44.8 ± 123.2 mg/g and none was dialyzed. In conclusion, living kidney donation does not impact survival, kidney function, medical condition or psychological or social status over the very long-term (read more).

The Montreal Criteria for the Ethical Feasibility of Uterine Transplantation

2012-02-23T09:22:00.000+01:00

Absolute uterine factor infertility (UFI) refers to the refractory causes of female infertility stemming from the anatomical or physiological inability of a uterus to sustain gestation. Today, uterine factor infertility affects 3–5% of the population. Traditionally, although surrogacy and adoption have been the only viable options for females affected by this condition, the uterine transplant is currently under investigation as a potential medical alternative for women who desire to go through the experience of pregnancy. Although animal models have shown promising results, human transplantation cases have only been described in case reports and a successful transplant leading to gestation is yet to occur in humans. Notwithstanding the intricate medical and scientific complexities that a uterine transplant places on the medical minds of our time, ethical questions on this matter pose a similar, if not greater, challenge. In light of these facts, this article attempts to present the ethical issues in the context of experimentation and standard practice which surround this controversial and potentially paradigm-altering procedure; and given these, introduces “The Montreal Criteria for the Ethical Feasibility of Uterine Transplantation”, a set of proposed criteria required for a woman to be ethically considered a candidate for uterine transplantation (read more).

Human herpesvirus-6 infections in kidney, liver, lung, and heart transplantation: review

2012-02-23T09:21:00.000+01:00

Human herpesvirus-6 (HHV-6), which comprises of HHV-6A and HHV-6B, is a common infection after solid organ transplantation. The rate of HHV-6 reactivation is high, although clinical disease is not common. Only 1% of transplant recipients will develop clinical illness associated with HHV-6 infection, and most are ascribable to HHV-6B. Fever, myelosuppression, and end-organ disease, including hepatitis and encephalitis, have been reported. HHV-6 has also been associated with various indirect effects, including a higher rate of CMV disease, acute and chronic graft rejection, and opportunistic infection such as invasive fungal disease. All-cause mortality is increased in solid organ transplant recipients with HHV-6 infection. HHV-6 is somewhat unique among human viruses because of its ability to integrate into the host chromosome. The clinical significance of chromosomally integrated HHV-6 is not yet defined, although a higher rate of bacterial infection and allograft rejection has been suggested. The diagnosis of HHV-6 is now commonly made using nucleic acid testing for HHV-6 DNA in clinical samples, but this can be difficult to interpret owing to the common nature of asymptomatic viral reactivation. Treatment of HHV-6 is indicated in established end-organ disease such as encephalitis. Foscarnet, ganciclovir, and cidofovir have been used for treatment (read more).

Clinical and immunological features of very long-term survivors with a single renal transplant

2012-02-22T10:53:00.000+01:00

The aim of this study was to analyze the clinical and immunological features of the 56 still alive patients at our institution harboring a functional first renal transplant since more than 30 years. The mean post-transplant graft survival in all patients was 35.4 ± 3.1 years, the mean serum creatinine concentration was 128.7 ± 7 μmol/l, and the mean urinary protein concentration was 0.6 ± 0.5 g/l. Fifty-one percent of the patients had experienced cancer involving the skin (46.1%) and/or other tissues (28%). Hepatocarcinoma was diagnosed in 11% of the patients with chronic viral hepatitis B and/or C (48%). The 5-year patient survival rate (considered after the 30th transplantation anniversary) was 27% in patients presenting a tumor versus 87% in those tumor-free (P < 0.0001). The thymic output, the proportions of the memory and naïve T cell subsets, and the frequencies of EBV- and CMV-reactive, IFN-γ-producing T cells did not differ from those observed in more recently transplanted patients. These results suggest that the impact of chronic immunosuppression on some immune functions does not worsen over time and that the observed high prevalence of cancer in these patients may be related to the synergistic effects of decreased immunosurveillance and the time required for carcinogenesis (read more).

Proteasome inhibition by bortezomib: Effect on HLA-antibody levels and specificity in sensitized patients awaiting renal allograft transplantation.

2012-02-16T23:30:00.000+01:00

BACKGROUND: Sensitization to human leukocyte antigen (HLA) prolongs waiting list time and reduces allograft survival in solid organ transplantation. Current strategies for pretransplant desensitization are based on B-cell depletion and extracorporeal treatment. The proteasome inhibitor bortezomib allows direct targeting of the antibody-producing plasma cell and has been used in antibody-mediated rejection (AMR) and recipient desensitization with varying results. Here, we report the effect of bortezomib preconditioning on HLA antibody titers and specificity in highly sensitized patients awaiting renal allograft transplantation. PATIENTS AND METHODS: Two highly sensitized patients awaiting third kidney transplantation were given one cycle of bortezomib (1.3mg/m², days 1, 4, 8, 11), as part of recipient desensitization. Time-course and levels of anti-HLA antibodies, as well as specificity to previous transplant antigens were monitored by luminex technology. In addition, measles and tetanus toxoid immunoglobulin G (IgG) was measured. RESULTS: Following bortezomib, overall changes in IgG levels were small and no sustained reduction in anti-HLA class I or II antibody levels was observed over more than 100days of follow-up to both, donor specific and non-donor specific antigens. Moreover, anti-measles and -tetanus toxoid IgG levels remained unchanged. CONCLUSIONS: Bortezomib preconditioning alone does not result in sustained reduction of HLA antibody levels or alter protective immunity in sensitized patients. This supports the notion, that bortezomib requires activation of plasma cells, as in AMR, to effectively reduce HLA antibody production. Hence, in a pretransplant setting, combination strategies may be required to derive benefit from proteasome inhibition (read more)

Complications of Living Donor Hepatic Lobectomy–A Comprehensive Report

2012-02-16T23:25:00.000+01:00

A wider application of living donor liver transplantation is limited by donor morbidity concerns. An observational cohort of 760 living donors accepted for surgery and enrolled in the Adult-to-Adult Living Donor Liver Transplantation cohort study provides a comprehensive assessment of incidence, severity and natural history of living liver donation (LLD) complications. Donor morbidity (assessed by 29 specific complications), predictors, time from donation to complications and time from complication onset to resolution were measured outcomes over a 12-year period. Out of the 760 donor procedures, 20 were aborted and 740 were completed. Forty percent of donors had complications (557 complications among 296 donors), mostly Clavien grades 1 and 2. Most severe counted by complication category; grade 1 (minor, n = 232); grade 2 (possibly life-threatening, n = 269); grade 3 (residual disability, n = 5) and grade 4 (leading to death, n = 3). Hernias (7%) and psychological complications (3%) occurred >1 year postdonation. Complications risk increased with transfusion requirement, intraoperative hypotension and predonation serum bilirubin, but did not decline with the increased center experience with LLD. The probability of complication resolution within 1 year was overall 95%, but only 75% for hernias and 42% for psychological complications. This report comprehensively quantifies LLD complication risk and should inform decision making by potential donors and their caregivers (read more).

In Situ Detection of HY-Specific T Cells in Acute Graft-versus-Host Disease–Affected Male Skin after Sex-Mismatched Stem Cell Transplantation

2012-02-14T11:54:00.000+01:00

HY-specific T cells are presumed to play a role in acute graft-versus-host disease (aGVHD) after female-to-male stem cell transplantation (SCT). However, infiltrates of these T cells in aGVHD-affected tissues have not yet been reported. We evaluated the application of HLA-A2/HY dextramers for the in situ detection of HY-specific T cells in cryopreserved skin biopsy specimens. We applied the HLA-A2/HY dextramers on cryopreserved skin biopsy specimens from seven male HLA-A2+ pediatric patients who underwent stem cell transplantation with confirmed aGVHD involving the skin. The dextramers demonstrated the presence of HY-specific T cells. In skin biopsy specimens of three male recipients of female grafts, 68% to 78% of all skin-infiltrating CD8+ T cells were HY-specific, whereas these cells were absent in biopsy specimens collected from sex-matched patient–donor pairs. Although this study involved a small and heterogeneous patient group, our results strongly support the hypothesis that HY-specific T cells are actively involved in the pathophysiology of aGVHD after sex-mismatched stem cell transplantation (read more).

Granulocyte transfusions to treat invasive aspergillosis in a patient with severe aplastic anemia awaiting mismatched HPC transplantation

2012-02-10T12:41:00.001+01:00

This case illustrates that HLA alloimmunization can be a major complication of granulocyte transfusions, resulting in the development of donor-directed HLA antibodies. A previously compatible HPC component had to be discarded, necessitating collection of a second graft from a different donor (read more : free full text).

Allosensitization Rate of Male Patients Awaiting First Kidney Grafts After Leuko-Depleted Blood Transfusion

2012-02-10T12:29:00.000+01:00

Background. Blood transfusions are generally avoided for potential renal transplant recipients due to risk of human leukocyte antigen (HLA) allosensitization. Despite the near universal use of erythropoiesis-stimulating agents, there are still occasions when patients require blood transfusions for reasons such as resistance to erythropoiesis-stimulating agents or cardiovascular instability. The risk of allosensitization in renal patients is believed to be lower with leuko-depleted blood. We sought to quantify the risk of blood transfusion per se in male renal patients on the transplant waiting list for their first kidney graft, using sensitive solid phase antibody detection.
Method. Cross-sectional survey looking at the prevalence of HLA antibody detected using single antigen Luminex beads in male patients awaiting first renal transplantation.
Results. One hundred sixteen male patients awaiting their first kidney transplant were identified on our waiting list. Seven of the 42 patients (16.7%) who received at least one unit of leuko-depleted blood developed HLA antibody (HLAab). Of the remaining 74 patients without a history of transfusion, 3 (4.1%) were found to have HLAab. All the antibodies identified were directed against class I antigens. A history of blood transfusion gave a relative risk of 4.1 of developing HLAab (P=0.02).
Conclusion. Male patients awaiting their first organ transplant had a fourfold increased risk of developing HLA antibody if they had been previously transfused when compared with those who did not have a history of a transfusion. Transfusion even in the postleukodepletion era continues to pose a significant risk of sensitization (read more).

Current Status of Hepatocyte Transplantation

2012-02-10T12:16:00.000+01:00

Hepatocyte transplantation (HT) has been performed in patients with liver-based metabolic disease and acute liver failure as a potential alternative to liver transplantation. The results are encouraging in genetic liver conditions where HT can replace the missing enzyme or protein. However, there are limitations to the technique, which need to be overcome. Unused donor livers to isolate hepatocytes are in short supply and are often steatotic, although addition of N-acetylcysteine improves the quality of the cells obtained. Hepatocytes are cryopreserved for later use and this is detrimental to metabolic function on thawing. There are improved cryopreservation protocols, but these need further refinement. Hepatocytes are usually infused into the hepatic portal vein with many cells rapidly cleared by the innate immune system, which needs to be prevented. It is difficult to detect engraftment of donor cells in the liver, and methods to track cells labeled with iron oxide magnetic resonance imaging contrast agents are being developed. Methods to increase cell engraftment based on portal embolization or irradiation of the liver are being assessed for clinical application. Encapsulation of hepatocytes allows cells to be transplanted intraperitoneally in acute liver failure with the advantage of avoiding immunosuppression. Alternative sources of hepatocytes, which could be derived from stem cells, are needed. Mesenchymal stem cells are currently being investigated particularly for their hepatotropic effects. Other sources of cells may be better if the potential for tumor formation can be avoided. With a greater supply of hepatocytes, wider use of HT and evaluation in different liver conditions should be possible (read more).

Donor B-cell alloantibody deposition and germinal center formation are required for the development of murine chronic GVHD and bronchiolitis obliterans

2012-02-10T11:39:00.000+01:00

Chronic GVHD (cGVHD) poses a significant risk for HSCT patients. Preclinical development of new therapeutic modalities has been hindered by models with pathologic findings that may not simulate the development of human cGVHD. Previously, we have demonstrated that cGVHD induced by allogeneic HSCT after a conditioning regimen of cyclophosphamide and total-body radiation results in pulmonary dysfunction and airway obliteration, which leads to bronchiolitis obliterans (BO), which is pathognomonic for cGVHD of the lung. We now report cGVHD manifestations in a wide spectrum of target organs, including those with mucosal surfaces. Fibrosis was demonstrated in the lung and liver and was associated with CD4⁺ T cells and B220⁺ B-cell infiltration and alloantibody deposition. Donor bone marrow obtained from mice incapable of secreting IgG alloantibody resulted in less BO and cGVHD. Robust germinal center reactions were present at the time of cGVHD disease initiation. Blockade of germinal center formation with a lymphotoxin-receptor–immunoglobulin fusion protein suppressed cGVHD and BO. We conclude that cGVHD is caused in part by alloantibody secretion, which is associated with fibrosis and cGVHD manifestations including BO, and that treatment with a lymphotoxin-β receptor–immunoglobulin fusion protein could be beneficial for cGVHD prevention and therapy (read more).