Impact of HLA Mismatching on Incidence of Posttransplant Non-Hodgkin Lymphoma After Kidney Transplantation

The IPTA Nashville Consensus Conference on Post-Transplant lymphoproliferative disorders after solid organ transplantation in children: III - Consensus guidelines for Epstein-Barr virus load and other biomarker monitoring

The International Pediatric Transplant Association convened an expert consensus conference to assess current evidence and develop recommendations for various aspects of care relating to post-transplant lymphoproliferative disorders after solid organ transplantation in children. In this report from the Viral Load and Biomarker Monitoring Working Group, we reviewed the existing literature regarding the role of Epstein-Barr viral load and other biomarkers in peripheral blood for predicting the development of PTLD, for PTLD diagnosis, and for monitoring of response to treatment. Key recommendations from the group highlighted the strong recommendation for use of the term EBV DNAemia instead of "viremia" to describe EBV DNA levels in peripheral blood as well as concerns with comparison of EBV DNAemia measurement results performed at different institutions even when tests are calibrated using the WHO international standard. The working group concluded that either whole blood or plasma could be used as matrices for EBV DNA measurement; optimal specimen type may be clinical context dependent. Whole blood testing has some advantages for surveillance to inform pre-emptive interventions while plasma testing may be preferred in the setting of clinical symptoms and treatment monitoring. However, EBV DNAemia testing alone was not recommended for PTLD diagnosis. Quantitative EBV DNAemia surveillance to identify patients at risk for PTLD and to inform pre-emptive interventions in patients who are EBV seronegative pre-transplant was recommended. In contrast, with the exception of intestinal transplant recipients or those with recent primary EBV infection prior to SOT, surveillance was not recommended in pediatric SOT recipients EBV seropositive pre-transplant. Implications of viral load kinetic parameters including peak load and viral set point on pre-emptive PTLD prevention monitoring algorithms were discussed. Use of additional markers, including measurements of EBV specific cell mediated immunity was discussed but not recommended though the importance of obtaining additional data from prospective multicenter studies was highlighted as a key research priority.

Pediatric Kidney Transplantation: Cancer and Cancer Risk

Children with end-stage kidney disease (ESKD) face a lifetime of complex medical care, alternating between maintenance chronic dialysis and kidney transplantation. Kidney transplantation has emerged as the optimal treatment of ESKD for children and provides important quality of life and survival advantages. Although transplantation is the preferred therapy, lifetime exposure to immunosuppression among children with ESKD is associated with increased morbidity, including an increased risk of cancer. Following pediatric kidney transplantation, cancer events occurring during childhood or young adulthood can be divided into two broad categories: post-transplant lymphoproliferative disorders and non-lymphoproliferative solid tumors. This review provides an overview of cancer incidence, types, outcomes, and preventive strategies in this population.

Role of standard HLA mismatch in modifying associations between non-pharmacologic risk factors and solid organ malignancy after kidney transplantation

BACKGROUND

Human leukocyte antigen mismatch(es) (HLA-mm) between donors and recipients has not been extensively studied either as a risk factor for solid organ malignancy (SOM) or as a modifier of associations between nonpharmacologic risk factors and SOM in kidney transplant recipients (KTRs).

METHODS

In a secondary analysis from a previous study, 166,256 adult KTRs in 2000-2018 who survived the first 12 months post-transplant free of graft loss or malignancy were classified into 0, 1-3, and 4-6 standard HLA-mm cohorts. Multivariable cause-specific Cox regressions analyzed the risks of SOM and all-cause mortality (ac-mortality) in 5 years following the first KT year. Comparisons of associations between SOM and risk factors in HLA mismatch cohorts were made by estimating the ratios of adjusted hazard ratios.

RESULTS

Compared with 0 HLA-mm, 1-3 HLA-mm was not associated, and 4-6 HLA-mm was equivocally associated with increased risk of SOM [hazard ratio, (HR) = 1.05, 95%, confidence interval (CI) = 0.94-1.17 and HR = 1.11, 95% CI = 1.00-1.34, respectively]. Both 1-3 HLA-mm and 4-6 HLA-mm were associated with increased risk of ac-mortality compared with 0 HLA mm [hazard ratio (HR) = 1.12, 95%, Confidence Interval (CI) = 1.08-1.18) and (HR = 1.16, 95% CI = 1.09-1.22), respectively]. KTR's history of pre-transplant cancer, age 50-64, and >/=65 years were associated with increased risks of SOM and ac-mortality in all HLA mismatch cohorts. Pre-transplant dialysis >2 years, diabetes as the primary renal disease, and expanded or standard criteria deceased donor transplantation were risk factors for SOM in the 0 and 1-3 HLA-mm cohorts and of ac-mortality in all HLA-mm cohorts. KTRs male sex or history of previous kidney transplant was a risk factor for SOM in the 1-3 and 4-6 HLA-mm cohorts and of ac-mortality in all HLA-mm cohorts.

CONCLUSION

Direct association between SOM and the degree of HLA mismatching is equivocal and limited to the 4-6 HLA-mm stratum; however, the degree of HLA mismatching has significant modifying effects on the associations between specific nonpharmacologic risk factors and SOM in KTRs.

Corneal Endothelial-like Cells Derived from Induced Pluripotent Stem Cells for Cell Therapy

Corneal endothelial dysfunction is one of the leading causes of corneal blindness, and the current conventional treatment option is corneal transplantation using a cadaveric donor cornea. However, there is a global shortage of suitable donor graft material, necessitating the exploration of novel therapeutic approaches. A stem cell-based regenerative medicine approach using induced pluripotent stem cells (iPSCs) offers a promising solution, as they possess self-renewal capabilities, can be derived from adult somatic cells, and can be differentiated into all cell types including corneal endothelial cells (CECs). This review discusses the progress and challenges in developing protocols to induce iPSCs into CECs, focusing on the different media formulations used to differentiate iPSCs to neural crest cells (NCCs) and subsequently to CECs, as well as the characterization methods and markers that define iPSC-derived CECs. The hurdles and solutions for the clinical application of iPSC-derived cell therapy are also addressed, including the establishment of protocols that adhere to good manufacturing practice (GMP) guidelines. The potential risks of genetic mutations in iPSC-derived CECs associated with long-term in vitro culture and the danger of potential tumorigenicity following transplantation are evaluated. In all, this review provides insights into the advancement and obstacles of using iPSC in the treatment of corneal endothelial dysfunction.

Pathophysiology of Rejection in Kidney Transplantation

Kidney transplantation has been the optimal treatment for end-stage kidney disease for almost 70 years, with increasing frequency over this period. Despite the prevalence of the procedure, allograft rejection continues to impact transplant recipients, with consequences ranging from hospitalization to allograft failure. Rates of rejection have declined over time, which has been largely attributed to developments in immunosuppressive therapy, understanding of the immune system, and monitoring. Developments in these therapies, as well as an improved understanding of rejection risk and the epidemiology of rejection, are dependent on a foundational understanding of the pathophysiology of rejection. This review explains the interconnected mechanisms behind antibody-mediated and T-cell-mediated rejection and highlights how these processes contribute to outcomes and can inform future progress.

Keratinocyte Cancer Mortality in Kidney Transplant Recipients

BACKGROUND

Kidney transplant recipients are at increased risk of developing and dying from keratinocyte cancer. Risk factors for keratinocyte cancer death have not been previously described.

METHODS

In a cohort of kidney transplant recipients transplanted in Queensland 1995-2014, we identified keratinocyte cancer deaths by searching national transplant and state death registries to March 2020. Standardized keratinocyte cancer mortality rates and mortality ratios were calculated. We used a competing risks model to identify factors associated with keratinocyte cancer death and calculated relative risks (RRs) and 95% confidence intervals (CIs).

RESULTS

There were 562 deaths in 1866 kidney transplant recipients (62% males; 86% Caucasian) with 25 934 person-years of follow-up, of which 36 were due to squamous cell carcinoma (SCC) and 1 to basal cell carcinoma (BCC) with standardized mortality rates of 78 (95% CI 53-111) and 2 (95% CI 0.1-11) per 100,000 person-years respectively. The standardized mortality ratio for keratinocyte cancer was 23 (95% CI 23-24). Besides Caucasian ethnicity (associated with 100% of keratinocyte cancer deaths), male sex (RR 3.24 95% CI 1.26-8.33), and older age at transplantation (≥ 50 versus <50 years RR 3.09 95% CI 1.38-6.89) were associated with increased risk of keratinocyte cancer death.

CONCLUSIONS

Keratinocyte cancer mortality in kidney transplant recipients is over 20 times higher than in the general population. Most keratinocyte cancer deaths are due to cutaneous SCC, however, BCC can be fatal. Education in skin cancer prevention is essential to avoid unnecessary deaths from keratinocyte cancer amongst kidney transplant recipients.

Risk factors evaluation of post-transplant lymphoproliferative disorders after allogeneic haematopoietic stem cell transplantation with comparison between paediatric and adult

To describe the clincopathological features and evaluate risk factors of post-transplant lymphoproliferative disorder (PTLD) after allogeneic haematopoietic stem cell transplants (allo-HSCT), with comparison between paediatric and adult .Clinicopathological features of 81 cases of PTLD after allo-HSCT were analysed by histopatholgy, immunohistochemistry and in situ hybridisatioin.The cases included 58 males and 23 females with a median age of 26.7 years (range 6-55 years) and the PTLDs developed 1-60 months post-transplant (mean 5.9 months). The histological types indicated 10 cases of non-destructive PTLD, including 4 of plasmacytic hyperplasia, 5 of infectious mononucleosis and 1 of florid follicular hyperplasia. Fifty-six cases were polymorphic PTLD, and 15 were monomorphic PTLD, including thirteen of diffuse large B cell lymphoma, 1 of extranodal nasal type natural killer (NK)/T cell lymphoma and 1 of plasmablastic lymphoma. Foci and sheets of necrosis were observed in 31 cases. The infected ratio of Epstein-Barr virus (EBV) was 91.4%. Some cases were treated by reduction of immunosuppression, antiviral therapy, donor lymphocyte infusion or anti-CD20 monoclonal rituximab. Thirty-three cases died. Compared with that of adult, overall survival of paediatric recipient may be better.The first half year after allo-HSCT is very important for the development of PTLD. Type of PTLD, EBV infection and graft-versus-host disease are risk factors. The prognosis of PTLD is poor, and PTLD after allo-HSCT exhibits some features different from that after solid organ transplantation and some differences existing between adult and paediatric recipients.

Association of HLA mismatch and MTOR inhibitor regimens with malignancy and mortality after kidney transplantation

Background The association of mammalian target of rapamycin inhibitors (MTORI) with malignancies and mortality in kidney transplant recipients (KTR) with different degrees of human leukocyte antigen mismatch (HLA-mm) at transplant has not been previously studied. Methods Our observational cohort study included 166, 256 adult KTRs in 2000-2018. Immunosuppression in the first post-transplant year were MTORIs in 13,056 (7.85%) and non-MTORIs in 153,200 (92.15%). We used Cox multivariable regression models to determine the cause-specific hazard ratio (HRcs) of non-melanoma skin cancer (NMSC),solid organ malignancies (SOM)] and all-cause death (death_ac); and the HR of the composite outcomes of NMSC or death_ac and SOM or death_ac associated with MTORI versus non-MTORI regimens in the overall study sample and the 0, 1-3, and 4-6 HLA-A, B and DR mm subgroups. Results NMSC risk was lower with MTORI than non-MTORI in all HLA-mm subgroups [(0 mm, HRcs = 0.67; 95% CI = 0.46-0.97, 1-3 mm, HRcs = 0.73; 95% CI = 0.61-0.87, 4-6 mm, HRcs = 0.69; 95% CI = 0.62-0.76)]. SOM risks were similar between regimens in the 0 HLA mm subgroup (HRcs = 1.10 (95% CI = 0.78-1.57) and lower with MTORI than non-MTORI in the 1-3, and 4-6 HLA-mm subgroups, [(HR = 0.84; (95% CI = 0.71-0.99), and (HR = 0.86; 95% CI = 0.78-0.94); respectively]. Risks of death_ac and composite outcomes (NMSC or death_ac and SOM or death_ac) were higher with MTORI than non-MTORI in almost all HLA-mm subgroups. Conclusion MTORIs are associated with protection from NMSC and SOM in almost all HLA-mm subgroups ca; however, their association with increased all-cause mortality in adult kidney transplant recipients needs further investigation.

Immunological Risk Factors in Paediatric Kidney Transplantation

Purpose

The aim of this study was to identify factors impacting recipient sensitization rates and paediatric renal transplant patient outcomes.

Patients and Methods

For this purpose, a retrospective analysis of 143 paediatric renal transplants was carried out. This included the evaluation of patient’s and donor’s demographic data, HLA mismatches, immunosuppressive therapy, rejection episodes, panel reactive antibody (PRA) and post-transplant lymphoproliferative disease (PTLD).

Results

The mean patient age at the point of transplant receival was 11.5 years with a mean follow up time of 9.33±5.05 years. It was noted that graft survival rates for donors over 59 years had the worst outcome. HLA match did not show statistically significant influence on graft outcome. Graft survival for more than one biopsy-proven rejection was also significantly shorter (p=0.008). PRA were found in 28% of the recipient’s post-transplantation and showed association with lower graft survival rates (p<0.001). In the present study, 22.7% (5/22) of the patients with EBV infections presented a PTLD.

Conclusion

In conclusion, good graft survival with reduced sensitization for future transplantations and minimize the risk of PTLD, can be ensured through a balance between donor age, HLA match and condition of the recipient should be sought. Furthermore, paediatric patients should preferably receive organs from donors between the age of 10 and 59. EBV infection could be a relevant factor for developing PTLD.

Retinal cell transplantation in retinitis pigmentosa

Retinitis pigmentosa is the most common hereditary retinal disease. Dietary supplements, neuroprotective agents, cytokines, and lately, prosthetic devices, gene therapy, and optogenetics have been employed to slow down the retinal degeneration or improve light perception. Completing retinal circuitry by transplanting photoreceptors has always been an appealing idea in retinitis pigmentosa. Recent developments in stem cell technology, retinal imaging techniques, tissue engineering, and transplantation techniques have brought us closer to accomplish this goal. The eye is an ideal organ for cell transplantation due to a low number of cells required to restore vision, availability of safe surgical and imaging techniques to transplant and track the cells in vivo, and partial immune privilege provided by the subretinal space. Human embryonic stem cells, induced pluripotential stem cells, and especially retinal organoids provide an adequate number of cells at a desired developmental stage which may maximize integration of the graft to host retina. However, stem cells must be manufactured under strict good manufacturing practice protocols due to known tumorigenicity as well as possible genetic and epigenetic stabilities that may pose a danger to the recipient. Immune compatibility of stem cells still stands as a problem for their widespread use for retinitis pigmentosa. Transplantation of stem cells from different sources revealed that some of the transplanted cells may not integrate the host retina but slow down the retinal degeneration through paracrine mechanisms. Discovery of a similar paracrine mechanism has recently opened a new therapeutic path for reversing the cone dormancy and restoring the sight in retinitis pigmentosa.

Cell-Based Therapies for Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness worldwide. The pathogenesis of AMD involves dysfunction and loss of the retinal pigment epithelium (RPE), a monolayer of cells that provide nourishment and functional support for the overlying photoreceptors. RPE cells in mammals are not known to divide, renew or regenerate in vivo, and in advanced AMD, RPE loss leads to degeneration of the photoreceptors and impairment of vision. One possible therapeutic approach would be to support and replace the failing RPE cells of affected patients, and indeed moderate success of surgical procedures in which relatively healthy autologous RPE from the peripheral retina of the same eye was transplanted under the retina in the macular area suggested that RPE replacement could be a means to attenuate photoreceptor cell loss. This prompted exploration of the possibility to use pluripotent stem cells (PSCs) as a potential source for "healthy and young" RPE cells for such cell-based therapy of AMD. Various approaches ranging from the use of allogeneic embryonic stem cells to autologous induced pluripotent stem cells are now being tested within early clinical trials. Such PSC-derived RPE cells are either injected into the subretinal space as a suspension, or transplanted as a monolayer patch upon scaffold support. Although most of these approaches are at early clinical stages, safety of the RPE product has been demonstrated by several of these studies. Here, we review the concept of cell-based therapy of AMD and provide an update on current progress in the field of RPE transplantation.

Critical evaluation of a possible role of HLA epitope matching in kidney transplantation

Human leukocyte antigen (HLA) matching is one of the cornerstones of organ allocation in deceased-donor kidney transplantation. Increased numbers of HLA allele mismatches are associated with a higher risk of immunological rejection, de novo donor-specific HLA antibody development and graft failure. HLA epitopes are defined as the specific portions of HLA molecules to which antibodies and T-cell receptors bind with their paratopes. The same epitope can be present on different HLA alleles. Therefore, HLA matching at the epitope instead of allele level theoretically offers a more precise assessment of donor-recipient HLA compatibility and may more effectively prevent sensitization against foreign tissue. In this review, we describe the different options proposed to define clinically relevant HLA epitopes and critically discuss the potential role of HLA epitope matching in kidney transplantation.

Incidence and predictors of post-transplant lymphoproliferative disease after kidney transplantation during adulthood and childhood: a registry study

Background

Differences in the epidemiology of post-transplant lymphoproliferative disease (PTLD) between adult and paediatric kidney transplant recipients remain unclear.

Methods

Using the Australian and New Zealand Dialysis and Transplant Registry (1963-2015), the cumulative incidences of PTLD in children (age <20 years) and adults were calculated using a competing risk of death model and compared with age-matched population-based data using standardized incidence ratios (SIRs). Risk factors for PTLD were assessed using Cox proportional hazards regression.

Results

Among 23 477 patients (92% adult, 60% male), 505 developed PTLD, with 50 (10%) occurring in childhood recipients. The 25-year cumulative incidence of PTLD was 3.3% [95% confidence interval (CI) 2.9-3.6] for adult recipients and 3.6% (95% CI 2.7-4.8) for childhood recipients. Childhood recipients had a 30-fold increased risk of lymphoma compared with the age-matched general population [SIR 29.5 (95% CI 21.9-38.8)], higher than adult recipients [SIR 8.4 (95% CI 7.7-9.2)]. Epstein-Barr virus (EBV)-negative recipient serology [adjusted hazard ratio (aHR) 3.33 (95% CI 2.21-5.01), P < 0.001], year of transplantation [aHR 0.93 for each year after the year 2000 (95% CI 0.88-0.99), P = 0.02], induction with an agent other than anti-CD25 monoclonal antibody [aHR 2.07 (95% CI 1.16-3.70), P = 0.01] and having diabetes [aHR 3.49 (95% CI 2.26-5.38), P < 0.001] were independently associated with PTLD.

Conclusions

Lymphoma occurs at similar rates in adult and paediatric recipients, but has been decreasing since the year 2000. EBV-negative patients and those with diabetes or induction agent other than anti-CD25 monoclonal antibody are at substantially increased risk of PTLD.

Clinical Prognosis of Renal Retransplant Patients: A Single-Center Experience

BACKGROUND

Retransplantation is a treatment option in patients with end-stage renal failure due to graft loss. Outcomes of these patients due to high immunologic risk remain unclear. The aim of this study was to evaluate outcomes of renal retransplantation patients retrospectively.

METHODS

Renal retransplant patients in our unit were evaluated retrospectively between 2010 and 2018. Patients' demographic characteristics, primary diseases, the causes of prior graft loss, immunologic status, desensitization protocols, the induction and maintenance treatments, the complications during the follow-up period, numbers of acute rejections, and the clinical prognosis were all detected from the patients' files.

RESULTS

We retrospectively evaluated 17 patients who underwent a second or third renal allograft. Of these, 16 received a second and the remaining 1 patient received a third renal allograft. Immunologically, all of the 17 patients had negative flow cytometry crossmatch, 1 patient had a positive complement-dependent cytotoxicity crossmatch (Auto 12%), 16 patients had positive panel reactive antibody, the median HLA-mismatch was 3.5, and the score of donor-specific antibody relative intensity score (RIS) was 6.4 ± 6.3. Ten pretransplant patients had desensitization treatment. While scores for HLA-MM and HLA-RIS in the patients who had a desensitization therapy were determined higher, no statistical difference was observed (respectively, P = .28 and .55). No acute rejection episode developed. BK virus DNA viremia was detected in 4 patients during the posttransplant 6th month. We observed no patient death or no graft loss during the follow-up period.

CONCLUSION

Although the retransplant patients who had a graft loss previously have high immunologic risks, retransplantation is reliable in these patients, but they should be followed up carefully in terms of BKV nephropathy.

Infection in Kidney Transplant Recipients

In organ transplant recipients, impaired inflammatory responses suppress the clinical and radiologic findings of infection. The possible etiologies of infection are diverse, ranging from common bacterial and viral pathogens that affect the entire community to opportunistic pathogens that cause invasive disease only in immunocompromised hosts. Antimicrobial therapies required to treat established infection are often complex, with accompanying risks for drug toxicities and drug interactions with the immunosuppressive agents used to maintain graft function. Rapid and specific diagnosis is essential for successful therapy. The risk of serious infections in the organ transplant patient is largely determined by the interaction between two factors: the patient’s epidemiologic exposures and the patient’s net state of immunosuppression. The epidemiology of infection includes environmental exposures and nosocomial infections, organisms derived from donor tissues, and latent infections from the recipient activated with immunosuppression. The net state of immune suppression is a conceptual framework that measures those factors contributing to risk for infection: the dose, duration, and temporal sequence of immunosuppressive drugs; the presence of foreign bodies or injuries to mucocutaneous barriers; neutropenia; metabolic abnormalities including diabetes; devitalized tissues, hematomas, or effusions postsurgery; and infection with immunomodulating viruses. Multiple factors are present in each host. A timeline exists to aid in the development of a differential diagnosis for infection. The timeline for each patient is altered by changes in prophylaxis and immunosuppressive drugs. For common infections, new microbiologic assays, often nucleic acid based, are useful in the diagnosis and management of opportunistic infections.

Toward the development of true "off-the-shelf" synthetic T-cell immunotherapy

Recent outstanding clinical results produced by engineered T cells, including chimeric antigen receptors, have already facilitated further research that broadens their applicability. One such direction is to explore new T cell sources for allogeneic “off‐the‐shelf” adoptive immunotherapy. Human pluripotent stem cells could serve as an alternative cell source for this purpose due to their unique features of infinite propagation ability and pluripotency. Here, we describe the current state of engineered T cell transfer with the focus on cell manufacturing processes and the potentials and challenges of induced pluripotent stem cell‐derived T cells as a starting material to construct off‐the‐shelf T‐cell banks.

Analysis of Risk Factors for Kidney Retransplant Outcomes Associated with Common Induction Regimens: A Study of over Twelve-Thousand Cases in the United States

We studied registry data of 12,944 adult kidney retransplant recipients categorized by induction regimen received into antithymocyte globulin (ATG) (N = 9120), alemtuzumab (N = 1687), and basiliximab (N = 2137) cohorts. We analyzed risk factors for 1-year acute rejection (AR) and 5-year death-censored graft loss (DCGL) and patient death. Compared with the reference, basiliximab: (1) one-year AR risk was lower with ATG in retransplant recipients of expanded criteria deceased-donor kidneys (HR = 0.56, 95% CI = 0.35-0.91 and HR = 0.54, 95% CI = 0.27-1.08, resp.), while AR risk was lower with alemtuzumab in retransplant recipients with >3 HLA mismatches before transplant (HR = 0.63, 95% CI = 0.44-0.93 and HR = 0.81, 95% CI = 0.63-1.06, resp.); (2) five-year DCGL risk was lower with alemtuzumab, not ATG, in retransplant recipients of African American race (HR = 0.54, 95% CI = 0.34-0.86 and HR = 0.73, 95% CI = 0.51-1.04, resp.) or with pretransplant glomerulonephritis (HR = 0.65, 95% CI = 0.43-0.98 and HR = 0.82, 95% CI = 0.60-1.12, resp.). Therefore, specific risk factor-induction regimen combinations may predict outcomes and this information may help in individualizing induction in retransplant recipients.

HLA and Risk of Diffuse Large B cell Lymphoma After Solid Organ Transplantation

BACKGROUND

Solid organ transplant recipients have heightened risk for diffuse large B cell lymphoma (DLBCL). The role of donor-recipient HLA mismatch and recipient HLA type on DLBCL risk are not well established.

METHODS

We examined 172 231 kidney, heart, pancreas, and lung recipients transplanted in the United States between 1987 and 2010, including 902 with DLBCL. Incidence rate ratios (IRRs) were calculated using Poisson regression for DLBCL risk in relation to HLA mismatch, types, and zygosity, adjusting for sex, age, race/ethnicity, year, organ, and transplant number.

RESULTS

Compared with recipients who had 2 HLA-DR mismatches, those with zero or 1 mismatch had reduced DLBCL risk, (zero: IRR, 0.76, 95% confidence interval [95% CI], 0.61-0.95; one: IRR, 0.83; 95% CI, 0.69-1.00). In stratified analyses, recipients matched at either HLA-A, -B, or -DR had a significantly reduced risk of late-onset (>2 years after transplantation), but not early-onset DLBCL, and there was a trend for decreasing risk with decreasing mismatch across all 3 loci (P = 0.0003). Several individual recipient HLA-A, -B, -C, -DR, and -DQ antigens were also associated with DLBCL risk, including DR13 (IRR, 0.74; 95% CI, 0.57-0.93) and B38 (IRR, 1.48; 95% CI, 1.10-1.93), confirming prior findings that these 2 antigens are associated with risk of infection-associated cancers.

CONCLUSIONS

In conclusion, variation in HLA is related to susceptibility to DLBCL, perhaps reflecting intensity of immunosuppression, control of Epstein-Barr virus infection among transplant recipients or chronic immune stimulation.

Peak panel reactive antibody, cancer, graft, and patient outcomes in kidney transplant recipients

BACKGROUND

High levels of pretransplant panel reactive antibodies (PRA) are known to be associated with detrimental effects on graft outcomes, but the association between pretransplant PRA levels and long-term patient outcomes is unclear.

METHODS

Using the Australian and New Zealand Dialysis and Transplant Registry (ANZDATA), we assessed the risk of rejection, graft failure, mortality and cancer in kidney transplant recipients with varying peak PRA levels.

RESULTS

In 7,118 kidney transplant recipients between 1997 and 2009, there were a total of 3,171 (44.6%), 3,306 (46.4%), 323 (4.5%), and 318 (4.5%) recipients with peak PRA levels of 0%, 1% to 50%, 51% to 80%, and greater than 80%, respectively. Compared to recipients with 0% peak PRA level, recipients with peak PRA levels greater than 80% were at increased risk of acute rejection (odds ratio, 1.81, 95% confidence interval [95% CI], 1.30-2.35; P < 0.001), death censored graft failure (hazard ratio [HR], 2.06; 95% CI, 1.46-2.91; P < 0.001), all-cause mortality (HR, 1.56; 95% CI, 1.15-2.11; P < 0.001) and cancer (HR, 1.94; 95% CI, 1.26-2.97; P = 0.002) in the adjusted models independent of human leukocyte antigen mismatches and initial immunosuppression.

CONCLUSION

Highly sensitized kidney transplant recipients with peak PRA greater than 80% had a greater risk of rejection, graft failure, cancer and death independent of age and time on dialysis. Strategies to reduce transplant waiting time and avoidance of sensitization in all potential transplant candidates are imperative to improve the overall graft and patient survival.

HLA Associations and Risk of Posttransplant Lymphoproliferative Disorder in a Danish Population-Based Cohort

BACKGROUND

Posttransplant lymphoproliferative disorder (PTLD) is a feared complication to organ transplantation, associated with substantial morbidity and inferior survival. Risk factors for PTLD include T cell-depleting induction therapy and primary infection or reactivation of Epstein-Barr virus. Possible associations between certain HLA types and the risk of developing PTLD have been reported by other investigators; however, results are conflicting.

METHODS

We conducted a retrospective, population-based study on 4295 Danish solid organ transplant patients from the Scandiatransplant database. Having identified 93 PTLD patients in the cohort, we investigated the association of HLA types with PTLD, Epstein-Barr virus status and time to PTLD onset. The outcomes survival and PTLD were evaluated using Cox regression; mismatching, and the PTLD-specific mortality were evaluated in a competing risk analysis.

RESULTS

Risk of PTLD was associated with male sex (odds ratio, 1.70; 95% confidence interval, 1.07-2.71), and, in women, HLA-DR13 conferred an increased risk (odds ratio, 3.22; 95% confidence interval, 1.41-7.31). In multivariate analysis, HLA-B45 and HLA-DR13 remained independent predictive factors of PTLD. Mismatching in the B locus was associated with a reduced risk of PTLD (P < 0.001). Overall survival was poor after a PTLD diagnosis and was significantly worse than that in the remaining transplant cohort (P < 0.001).

CONCLUSIONS

Our data indicate risk-modifying HLA associations, which can be clinically useful after transplantation in personalized monitoring schemes. Given the strong linkage disequilibrium in the HLA region, the associations must be interpreted carefully. The large size, virtually complete ascertainment of cases and no loss to follow-up remain important strengths of the study.

New directions for rabbit antithymocyte globulin (Thymoglobulin(®)) in solid organ transplants, stem cell transplants and autoimmunity

In the 30 years since the rabbit antithymocyte globulin (rATG) Thymoglobulin^® was first licensed, its use in solid organ transplantation and hematology has expanded progressively. Although the evidence base is incomplete, specific roles for rATG in organ transplant recipients using contemporary dosing strategies are now relatively well-identified. The addition of rATG induction to a standard triple or dual regimen reduces acute cellular rejection, and possibly humoral rejection. It is an appropriate first choice in patients with moderate or high immunological risk, and may be used in low-risk patients receiving a calcineurin inhibitor (CNI)-sparing regimen from time of transplant, or if early steroid withdrawal is planned. Kidney transplant patients at risk of delayed graft function may also benefit from the use of rATG to facilitate delayed CNI introduction. In hematopoietic stem cell transplantation, rATG has become an important component of conventional myeloablative conditioning regimens, following demonstration of reduced acute and chronic graft-versus-host disease. More recently, a role for rATG has also been established in reduced-intensity conditioning regimens. In autoimmunity, rATG contributes to the treatment of severe aplastic anemia, and has been incorporated in autograft projects for the management of conditions such as multiple sclerosis, Crohn’s disease, and systemic sclerosis. Finally, research is underway for the induction of tolerance exploiting the ability of rATG to induce immunosuppresive cells such as regulatory T-cells. Despite its long history, rATG remains a key component of the immunosuppressive armamentarium, and its complex immunological properties indicate that its use will expand to a wider range of disease conditions in the future.

Use of pharmacogenomics in pediatric renal transplant recipients

Transplant recipients receive potent immunosuppressive drugs in order to prevent graft rejection. Therapeutic drug monitoring is the current approach to guide the dosing of calcineurin inhibitors, mammalian target of rapamycin inhibitors (mTORi) and mofetil mycophenolate. Target concentrations used in pediatric patients are extrapolated from adult studies. Gene polymorphisms in metabolizing enzymes and drug transporters such as cytochromes CYP3A4 and CYP3A5, UDP-glucuronosyl transferase, and P-glycoprotein are known to influence the pharmacokinetics and dose requirements of immunosuppressants. The implications of pharmacogenomics in this patient population is discussed. Genetic information can help with achieving target concentrations in the early post-transplant period, avoiding adverse drug reactions and drug-drug interactions. Evidence about genetic studies and transplant outcomes is revised.

Potential and limitation of HLA-based banking of human pluripotent stem cells for cell therapy

Great hopes have been placed on human pluripotent stem (hPS) cells for therapy. Tissues or organs derived from hPS cells could be the best solution to cure many different human diseases, especially those who do not respond to standard medication or drugs, such as neurodegenerative diseases, heart failure, or diabetes. The origin of hPS is critical and the idea of creating a bank of well-characterized hPS cells has emerged, like the one that already exists for cord blood. However, the main obstacle in transplantation is the rejection of tissues or organ by the receiver, due to the three main immunological barriers: the human leukocyte antigen (HLA), the ABO blood group, and minor antigens. The problem could be circumvented by using autologous stem cells, like induced pluripotent stem (iPS) cells, derived directly from the patient. But iPS cells have limitations, especially regarding the disease of the recipient and possible difficulties to handle or prepare autologous iPS cells. Finally, reaching standards of good clinical or manufacturing practices could be challenging. That is why well-characterized and universal hPS cells could be a better solution. In this review, we will discuss the interest and the feasibility to establish hPS cells bank, as well as some economics and ethical issues.

A de novo monoclonal immunoglobulin deposition disease in a kidney transplant recipient: a case report

Introduction

Myeloma following kidney transplantation is a rare entity. It can be divided into two groups: relapse of a previous myeloma and de novo myeloma. Some of these myelomas can be complicated by a monoclonal immunoglobulin deposition disease, which is even less common. Less than ten cases of monoclonal immunoglobulin deposition disease after renal graft have been reported in the literature. The treatment of these patients is not well codified.

Case presentation

We report the case of a 43-year-old white European man who received a renal transplant for a nephropathy of unknown etiology and developed a nephrotic syndrome with kidney failure at 2-years follow-up. We diagnosed a de novo monoclonal immunoglobulin deposition disease associated with a kappa light chain multiple myeloma, which is a very uncommon presentation for this disease. Three risk factors were identified in this patient: Epstein–Barr virus reactivation with cytomegalovirus co-infection; intensified immunosuppressive therapy during two previous rejection episodes; and human leukocyte antigen-B mismatches. Chemotherapy treatment and decrease in the immunosuppressive therapy were followed by remission and slight improvement of renal function. A relapse occurred 8 months later and his renal function worsened rapidly requiring hemodialysis. He died from septic shock 4 years after the diagnosis of monoclonal immunoglobulin deposition disease.

Conclusions

This rare case of post-transplant lymphoproliferative disorder with an uncommon presentation illustrates the fact that treatment in such a situation is very difficult to manage because of a small number of patients reported and a lack of information on this disease. There are no guidelines, especially concerning the immunosuppressive therapy management.

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.

Current role of human leukocyte antigen matching in kidney transplantation

PURPOSE OF REVIEW

With graft survival rates steadily improving during the recent years, there is debate whether donor kidneys should still be allocated according to compatibility for human leukocyte antigens (HLA).

RECENT FINDINGS

Recent studies argue for continued kidney exchange efforts for achieving better HLA compatibility. In this modern era of immunosuppression, better HLA matching is associated not only with better graft survival, but also with the administration of lower dosages of immunosuppressive agents, a lower incidence of side-effects of immunosuppression such as non-Hodgkin lymphoma, hip fractures, and death from infection, and a lower grade of sensitization if a patient has lost a kidney graft and is relisted for a retransplant.

SUMMARY

Despite the overall improved graft survival rates in the recent years, the data continue to support organ sharing based on HLA matching in kidney transplantation.

HLA compatibility index: does it have a role in patients after heart transplantation?

AIMS

To determine the impact of HLA compatibility measured by the Compatibility Index, on survival, rate of rejections, malignancies and infections in patients after heart transplantation (HTx).

METHODS

We carried out a retrospective analysis of 182 consecutive patients who underwent heart transplantation in our center from January 2001 to April 2010. According to degree of HLA-A, B and DR matching (Compatibility Index, CI) the patients were divided in two groups, Group A (n=83) with an IC 0-17 and group B (n=99) with an IC 18-26. There was no significant difference in demographic parameters between recipients and donors.

RESULTS

We found no difference in rates of rejections or infections between Group A and Group B (AR: 22 (26.5%) vs. 34 (34.3%), P=0.2539; infections: 21 (25.3%) vs. 27 (27%) P=0.7637). The distribution of infections in terms of type (bacterial, viral, fungal, including Aspergillus) was similar in both groups. The incidence of malignant tumours was infrequent (3 (3.6%) vs. 4 (4.0%), P=0.8817). We found trend toward lower level of tacrolimus in Group A. Long term survival was similar in both groups.

CONCLUSIONS

Based on the results of our single-center trial, we found no impact of higher degree of HLA-A,-B, and -DR matching on survival, rejection episodes or infection. Further large studies are necessary to confirm our hypothesis that subjects with better HLA compatibility could require lower dose immunosuppression.

Generating an iPSC bank for HLA-matched tissue transplantation based on known donor and recipient HLA types

The likelihood for immunological rejection of Human Leukocyte Antigens (HLA)-mismatched induced pluripotent stem cells (iPSCs) limits their therapeutic potential. Here we show how a tissue bank from 150 selected homozygous HLA-typed volunteers could match 93% of the UK population with a minimal requirement for immunosuppression. Our model provides a practical approach for using existing HLA-typed samples to generate an iPSC stem cell bank that circumvents prospective typing of a large number of individuals.

A glow of HLA typing in organ transplantation

The transplant of organs and tissues is one of the greatest curative achievements of this century. In organ transplantation, the adaptive immunity is considered the main response exerted to the transplanted tissue, since the main goal of the immune response is the MHC (major histocompatibility complex) molecules expressed on the surface of donor cells. Cell surface molecules that induce an antigenic stimulus cause the rejection immune response to grafted tissue or organ. A wide variety of transplantation antigens have been described, including the major histocompatibility molecules, minor histocompatibility antigens, ABO blood group antigens and endothelial cell antigens. The sensitization to MHC antigens may be caused by transfusions, pregnancy, or failed previous grafts leading to development of anti-human leukocyte antigen (HLA) antibodies that are important factor responsible for graft rejection in solid organ transplantation and play a role in post-transfusion complication Anti-HLA Abs may be present in healthy individuals. Methods for HLA typing are described, including serological methods, molecular techniques of sequence-specific priming (SSP), sequence-specific oligonucleotide probing (SSOP), Sequence based typing (SBT) and reference strand-based conformation analysis (RSCA) method. Problems with organ transplantation are reservoir of organs and immune suppressive treatments that used to decrease rate of rejection with less side effect and complications.

Association of HLA mismatch with death with a functioning graft after kidney transplantation: a collaborative transplant study report

HLA mismatches may correlate with risk of death with a functioning graft (DWFG) because of requirement for higher immunosuppression doses and more antirejection therapy. Deceased-donor kidney transplants (n = 177 584) performed 1990-2009 and reported to the Collaborative Transplant Study were analyzed. The incidence of DWFG was found to be 4.8% during year 1 posttransplant and 7.7% during years 2-5 (Kaplan-Meier estimates). Most frequent causes of DWFG were infection, cardiovascular disease and malignancy (32.2%, 30.9% and 3.6% in year 1; 16.4%, 29.6% and 15.9% in years 2-5). HLA-A + B + DR mismatches were significantly associated with DWFG during year 1 (p < 0.001), a correlation that diminished but persisted during years 2-5 (p < 0.001). HLA mismatch was associated with DWFG because of infection (p < 0.001 during year 1, p = 0.043 during years 2-5) or cardiovascular disease (p < 0.001 during year 1, p = 0.030 during years 2-5) but not malignancy. There was also a significant association between HLA mismatch and hospitalization for viral (p < 0.001) or bacterial (p = 0.002) infection. Multivariable analysis showed that mismatches for HLA class II were more strongly associated with both hospitalization and DWFG than mismatches for HLA class I.

Managing post-transplant lymphoproliferative disorders in solid-organ transplant recipients: a review of immunosuppressant regimens

Post-transplant lymphoproliferative disorders (PTLD) are a heterogeneous group of potentially life-threatening complications that occur after solid organ and bone marrow transplantation. Risk factors for acquiring PTLD are type of organ transplanted, age, intensity of immunosuppression, viral infections such as Epstein-Barr virus (EBV) and time after transplantation. Due to a dearth of well designed prospective trials, treatment for PTLD is often empirical, with reduction in immunosuppression accepted as the first step. Rituximab, a monoclonal antibody directed against the CD20 antigen of immature B cells, is often used as monotherapy after reduction in immunosuppression, although this is associated with a high risk of relapse if patients have at least one of the following risk factors: age greater than 60 years, elevated lactate dehydrogenase levels and Eastern Cooperative Oncology Group Score between 2 and 4. For such patients, rituximab should be considered in combination with CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone), particularly if high-grade PTLD is present. Although widely prescribed, the use of ganciclovir for PTLD remains controversial as EBV-transformed cells lack the thymidine kinase necessary for ganciclovir activation. Newer antivirals that combine ganciclovir with activators of cellular thymidine kinase have shown promising results in preclinical studies. In the absence of controlled trials, surgery may be indicated for localized disease and radiotherapy for patients with impending spinal cord compression or disease localized to the central nervous system or orbit. Future interventions may include adoptive immunotherapy, intravenous immunoglobulin, mammalian target of rapamycin inhibitors, monoclonal antibodies to interleukin-6 and galectin-1, and even EBV vaccination. Although several trials are in progress, it is necessary to wait for the long-term outcome of these studies on risk of PTLD relapse.

New concepts and best practices for management of pre- and post-transplantation cancer

Solid-organ transplant recipients are at increased risk of developing cancer compared with the general population. Tumours can arise de novo, as a recurrence of a preexisting malignancy, or from the donated organ. The ATOS (Aula sobre Trasplantes de Órganos Sólidos; the Solid-Organ Transplantation Working Group) group, integrated by Spanish transplant experts, meets annually to discuss current advances in the field. In 2011, the 11th edition covered a range of new topics on cancer and transplantation. In this review we have highlighted the new concepts and best practices for managing cancer in the pre-transplant and post-transplant settings that were presented at the ATOS meeting. Immunosuppression plays a major role in oncogenesis in the transplant recipient, both through impaired immunosurveillance and through direct oncogenic activity. It is possible to transplant organs obtained from donors with a history of cancer as long as an effective minimization of malignancy transmission strategy is followed. Tumour-specific wait-periods have been proposed for the increased number of transplantation candidates with a history of malignancy; however, the patient's individual risk of death from organ failure must be taken into consideration. It is important to actively prevent tumour recurrence, especially the recurrence of hepatocellular carcinoma in liver transplant recipients. To effectively manage post-transplant malignancies, it is essential to proactively monitor patients, with long-term intensive screening programs showing a reduced incidence of cancer post-transplantation. Proposed management strategies for post-transplantation malignancies include viral monitoring and prophylaxis to decrease infection-related cancer, immunosuppression modulation with lower doses of calcineurin inhibitors, and addition of or conversion to inhibitors of the mammalian target of rapamycin.

Compatibility and kidney transplantation: the way to go

Long lasting debates in the past questioned the relevance of any sort of compatibility in post mortal kidney transplantation. It is for no say that fully compatible transplants have the highest chances for a long patient and graft survival. In the present report the use of HLA-DR as a representative of the Major Histocompatibility Complex class II genes in the allocation of organs is discussed. The major arguments are the easiness to offer to patients a compatible graft in a relatively short waiting time, an increase in graft survival, the less sensitization during the transplantation period, and the lower waiting time for a retransplant. Even if the number of organ donors remains the same a lowering of the mean waiting time is expected because of the longer period of graft survival.

Epidemiology of posttransplant lymphoproliferative disorders in adult kidney and kidney pancreas recipients: report of the French registry and analysis of subgroups of lymphomas

A registry of posttransplant lymphoproliferative disorders (PTLD) was set up for the entire population of adult kidney transplant recipients in France. Cases of PTLD were prospectively enrolled between January 1, 1998, and December 31, 2007. Ten-year cumulative incidence was analyzed in patients transplanted after January 1, 1989. PTLD risk factors were analyzed in patients transplanted after January 1, 1998 by Cox analysis. Cumulative incidence was 1% after 5 years, 2.1% after 10 years. Multivariate analysis showed that PTLD was significantly associated with: older age of the recipient 47-60 years and >60 years (vs. 33-46 years, adjusted hazard ratio (AHR) = 1.87, CI = 1.22-2.86 and AHR = 2.80, CI = 1.73-4.55, respectively, p < 0.0001), simultaneous kidney-pancreas transplantation (AHR = 2.52, CI = 1.27-5.01 p = 0.008), year of transplant 1998-1999 and 2000-2001 (vs. 2006-2007, AHR = 3.36, CI = 1.64-6.87 and AHR = 3.08, CI = 1.55-6.15, respectively, p = 0.003), EBV mismatch (HR = 5.31, CI = 3.36-8.39, p < 0.001), 5 or 6 HLA mismatches (vs. 0-4, AHR = 1.54, CI = 1.12-2.12, p = 0.008), and induction therapy (AHR = 1.42, CI = 1-2.02, p = 0.05). Analyses of subgroups of PTLD provided new information about PTLD risk factors for early, late, EBV positive and negative, polymorphic, monomorphic, graft and cerebral lymphomas. This nationwide study highlights the increased risk of PTLD as long as 10 years after transplantation and the role of cofactors in modifying PTLD risk, particularly in specific PTLD subgroups.

On the future of HLA

As the immunobiological function of the HLA (human leucocyte antigen) class I and II molecules was revealed, we have seen an explosive development of the HLA field. Today, the HLA complex occupies a central position in basic and clinical immunology. In this Opinion article, I will briefly discuss some challenges which in my opinion are more important than others in the near future of HLA, with a focus on products of the classical HLA class I and II genes. Matching for HLA antigens will continue to be of importance in organ and hematopoietic stem cell transplantations. In the latter field, induction of graft-versus-leukemia effects will receive greater attention, where HLA will play a central role. It is anticipated that we will see an extensive development in our knowledge of the etiology and pathogenesis of autoimmune diseases, where some HLA class I and II genes by far are the strongest predisposing genes. To predict and prevent autoimmune diseases will be a major challenge for the HLA field in the future. HLA will also be of increasing importance in pharmacogenomics, vaccinations and anthropology. Together, this will leave the HLA field with many new challenges and opportunities, which in the future will require more focus on functional aspects of the immunogenetics of HLA.

Impact of HLA matching and HLA antibodies in organ transplantation: a collaborative transplant study view

The Collaborative Transplant Study (CTS) was initiated in 1982 in Heidelberg, Germany, and originated from the need to gain further insight into the complex problems and risks involved in human organ transplantation. Currently, more than 400 transplant centers in 45 countries are contributing to this voluntary international effort, and from the beginning of the study, the impact on graft outcome of immunological factors, such as matching for HLA antigens and allosensitization to HLA and non-HLA antigens, have been areas of interest. Herein, we summarize the recent findings from the CTS on these two topics.

Lymphoproliferative disorders after adult kidney transplant: epidemiology and comparison of registry report with claims-based diagnoses

BACKGROUND

Posttransplant lymphoproliferative disorder (PTLD) is a major complication of kidney transplant.

STUDY DESIGN

Retrospective cohort study comparing PTLD incidence rates using US Medicare claims and Organ Procurement and Transplantation Network (OPTN) data, examining risk factors for PTLD in OPTN data, and studying recipient and graft survival after PTLD diagnosis.

SETTING & PARTICIPANTS

All adult first-transplant patients who underwent deceased or living donor kidney-only transplants in 2000-2006 (n = 89,485) followed up through 3 years posttransplant.

PREDICTORS

Recipient and donor characteristics, HLA mismatches, viral serologic test results, and initial immunosuppression.

OUTCOMES

OPTN-reported or Medicare claims-based PTLD diagnosis, recipient and graft survival after OPTN-reported PTLD diagnosis.

MEASUREMENTS

Adjusted HRs for PTLD diagnosis estimated using a Cox proportional hazards model; probability of survival free of all-cause graft failure estimated using the Kaplan-Meier method.

RESULTS

The incidence rate of PTLD during the first posttransplant year was 2-fold higher in Medicare claims (0.46/100 patient-years; 95% CI, 0.39-0.53) than in OPTN data (0.22/100 patient-years; 95% CI, 0.17-0.27). Factors associated with increased rates of PTLD included older age, white race (vs African American), induction with T-cell-depleting antibodies, Epstein-Barr virus seronegativity at the time of transplant, and cytomegalovirus seronegativity at the time of transplant. The adjusted risk of death with graft function was 17.5 (95% CI, 14.3-21.4) times higher after a report of PTLD, and the risk of death-censored graft failure was 5.5 (95% CI, 3.9-7.7) times higher.

LIMITATIONS

Shortcomings inherent in large databases, including inconsistencies in patient follow-up, reporting, and coding practices by transplant centers; insufficient registry data to analyze acute rejection episodes and antirejection treatment; no available data for potential effects of different types of PTLD treatment on patient outcomes.

CONCLUSIONS

Despite the limitations of data collected by registries, PTLD clearly is an important complication; both mortality and death-censored graft failure increase after PTLD.

Association of mismatches for HLA-DR with incidence of posttransplant hip fracture in kidney transplant recipients

BACKGROUND

Bone fractures are a frequent complication after kidney transplantation, for which various predisposing factors have been identified. It has been suggested that human leukocyte antigen (HLA) mismatch increases the risk.

METHODS

Data on hip fractures occurring in the first 5 years posttransplant were analyzed among kidney transplants from deceased donors performed between 1995 and 2008 and reported to the Collaborative Transplant Study.

RESULTS

In the 20,509 patients analyzed, the cumulative rate of hip fracture by year 5 posttransplant was 0.85%. Cox regression analysis identified the following risk factors: female recipients aged 40 to 59 years (hazard ratio [HR] 2.26, P=0.029), female recipients 60 years or older (HR 5.14, P<0.001), male recipients 60 years or older (HR 2.39, P=0.028), and donor age more than or equal to 60 years (HR 1.75, P=0.009). Using the rate of fractures in recipients with zero HLA-DR mismatch as the reference, the risk of hip fracture increased for grafts with one HLA-DR mismatch to HR 1.85 (95% confidence interval [CI] 1.18-2.89, P=0.007) and with two HLA-DR mismatches to HR 2.24 (CI 1.25-4.02, P=0.007). There was a significant association between the number of HLA-DR mismatches and the diagnosis of osteoporosis 5 years after transplantation: one HLA-DR mismatch risk ratio 1.26 (CI 1.12-1.43, P<0.001) and two HLA-DR mismatches risk ratio 1.45 (CI 1.20-1.74, P<0.001).

CONCLUSION

The risk of hip fracture after kidney transplantation seems to be markedly exacerbated by HLA-DR mismatching. These findings add to the growing base of evidence that HLA-DR matching influences morbidity after kidney transplantation.

Post-transplant lymphoproliferative disorder in view of the new WHO classification: a more rational approach to a protean disease?

Post-transplant lymphoproliferative disorders (PTLDs) are serious, life-threatening complications of solid-organ transplantation (SOT) and bone marrow transplantation leading to a high mortality (30-60%). PTLD represents a heterogeneous group of lymphoproliferative diseases. They become clinically relevant because of the expansion of transplantation medicine together with the development of potent immunosuppressive drugs. Although the diagnostic morphological criteria of different forms of PTLD are commonly known, rapid and correct diagnosis is not always easy. Because of the limited number of clinical trials, a consensus is lacking on the optimal treatment of PTLD. This review focuses on incidence, risk factors, clinical picture of the disease and diagnostic tools including histopathology relating to the new classification introduced in 2008 by the World Health Organisation (WHO) and treatment of PTLD.