Clinical relevance of pre and post-transplant immune markers in kidney allograft recipients: Anti-HLA and MICA antibodies and serum levels of sCD30 and sMICA

Monitoring of Soluble Forms of BAFF System (BAFF, APRIL, sR-BAFF, sTACI and sBCMA) in Kidney Transplantation

BAFF system plays an essential role in B cells homeostasis and tolerance, although it has widely not been tested in transplantation with doubtful results. The main purpose was to study the BAFF soluble forms and their correlation with acute rejection (AR) and donor-specific antibodies production. Serum levels of BAFF, APRIL, and soluble forms of their receptors were analyzed in renal recipients with and without acute rejection (AR/NAR) appearance. All molecules were evaluated at pre- and post-transplantation. sTACI showed a significant correlation with BAFF and sR-BAFF levels, and sBCMA also showed a positive correlation with sAPRIL levels. A significant increase in sAPRIL levels in patients suffering AR was also found, and ROC curves analysis showed an AUC = 0.724, a concentration of 6.05 ng/ml (sensitivity: 66.7%; specificity: 73.3%), the best cutoff point for predicting AR. In the post-transplant dynamics of sAPRIL levels in the longitudinal cohort, we observed a significant decrease at 3 and 6 month post-transplantation compared to pretransplantation status. We also observed that recipients with high pre-transplant levels of sAPRIL generated antibodies earlier than those with lower sAPRIL levels, although their long-term post-transplantation was not different. Our results show that elevated serum levels of APRIL may be helpful as a biomarker for the diagnosis of AR, although the longitudinal study shows that it is not helpful as a prognostic biomarker.

Distribution of MICA alleles and haplotypes associated with HLA-B in Greek population

INTRODUCTION

The Major Histocompatibility Complex Class I-related chain A gene (MICA) is a highly polymorphic functional gene located close to the HLA-B locus. Certain MICA alleles have been related to inflammatory and autoimmune diseases while MICA antibodies have been implicated in organ allograft rejection or graft-versus-host disease (GVHD).

AIM

The aim of this study was to identify the frequencies of MICA alleles and MICA ~ HLA-B haplotypes in the Greek population since, as far as we know, these data are still limited.

METHODS

DNA was obtained from 277 unrelated healthy Greek individuals of Caucasian origin, volunteer donors of blood stem cells. HLA-B* and MICA* genotyping was performed by reverse PCR-SSOP.

RESULTS

A total of 18 MICA alleles were defined in the present study. The five most frequent alleles in the Greek population were MICA*008 (24.6%), MICA*009 (22.36%), MICA*018 (16.03%), MICA*002 (8.02%) and MICA*004 (7.17%) which altogether account for 77.8% of all alleles. The most common MICA ~ HLA-B haplotypes were MICA*018 ~ B*18 (12.5%) and MICA*009 ~ B*51(11.5%).

CONCLUSIONS

The five most frequent MICA alleles in the Greek population were *008, *009, *018, *002, *004. In other Caucasian populations, two of these alleles (*008, and *004) were observed in similar frequencies. MICA*002 was observed less frequently (8.02%) in the Greek population compared to other Caucasian groups (frequencies > 15%). Also, MICA*009 and MICA*018 had elevated frequencies (above 15%) whereas in other Caucasian populations they were found around 10% or less. These data may be important for the elucidation of the role that MICA polymorphisms play in organ and stem cell transplantation and to identify the relation of certain MICA with susceptibility to specific diseases.

Clinical relevance of major histocompatibility complex class I chain-related molecule A (MICA) antibodies in live donor renal transplantation - Indian Experience

Antibody-mediated rejections (AMR) in the absence of circulating anti-HLA-DSA have highlighted the role of non-HLA antibodies, particularly those directed against endothelial cells. Of these, MICA (major histocompatibility complex class I chain-related molecule A) antibodies are the most notable and important because of their potential in promoting graft rejections. Limited studies have focused on the impact of MICA donor-specific antibodies (DSA) on graft outcome as compared to those that are not donor-specific (NDSA). We evaluated pre- and post-transplant sera at POD 7, 30, 90, 180 and the time of biopsy from 206 consecutive primary live donor renal transplant recipients for anti-MICA and anti-HLA antibodies using single antigen bead assay on a Luminex platform. Recipients who developed MICA antibodies and their donors were phenotyped for MICA alleles. For the purpose of antibody analysis, patients were categorized into three major groups: biopsy-proven AMR, acute cellular rejection (ACR) and those with no rejection episodes (NRE). During the mean follow-up period of 17.37 ± 6.88 months, 16 of the 206 recipients developed AMR, while ACR was observed in only 13 cases. A quarter (25%) of the AMR cases had anti-MICA antibodies as compared to 7.7% of those experiencing ACR and 6.2% of the NRE group. Allelic typing revealed that all MICA Ab +ve AMR cases were due to the presence of donor-specific antibodies. MICA-DSA even in the absence of HLA-DSA was significantly associated with AMR but not with ACR when compared with the NRE group (P = <.01).

Soluble CD30, the Immune Response, and Acute Rejection in Human Kidney Transplantation: A Systematic Review and Meta-Analysis

Soluble CD30 (sCD30) is considered to be a marker for the activated immune system in which T cells can damage the allograft. Some studies reported that post-transplant sCD30 can predict early acute rejection and can thereby be used as a biomarker to detect acute rejection. However, several other studies found no relation between post-transplant sCD30 and acute rejection. This meta-analysis study aims to answer this main question of whether sCD30 can help clinicians to monitor transplant recipients. The electronic databases, including PubMed, Web of Science, ProQuest, Embase, Scopus, Google Scholar, the gray literature, and the key journals, were searched for observational studies from 1 January 1990 up to 30 April 2018. Eighteen studies, with a total of 1,453 patients, were included in this paper. With regard to the different measurement times, post-transplant sCD30 was separately analyzed and divided into five groups (i.e., 1, 2, 3, 4 week, and 1 month post-transplant sCD30). All groups indicated a strong association between sCD30 and the acute rejection. The standardized mean difference (SMD) is 1.22 in 1 week, 0.77 in 2 week, 1.11 in 3 week, 1.27 in 4 week, and 0.71 in 1 month groups. The association between sCD30 and acute rejection was consistent across all the subgroup analyses. We found that post-transplant sCD30 had a strong association with acute kidney rejection. We also found that the deceased donors had more association with the high amount of sCD30 than living donors in patients with acute rejection. Finally, we realized that donor type was an important factor leading to the heterogeneous results in the primary studies.

Role of Anti-MICA Antibodies in Graft Survival of Renal Transplant Recipients of India

INTRODUCTION

The MIC (MHC class I chain-related) genes are a group of nonclassical MHC genes, located in the MHC class 1 region of chromosome 6. The aim of the present study was to find the prevalence of MHC class 1 chain-related (MICA) alloantibodies in patients undergoing live-related donor renal transplantation and its role in short-term graft survival. The role of blood transfusion in the formation of these antibodies was also studied.

MATERIALS AND METHODS

Pretransplant samples of patients undergoing renal allograft transplantation were tested for anti-MICA antibodies. Association of various demographics, HLA-A + B + DRB1 mismatches, anti-HLA antibody screen, and anti-MICA antibodies was assessed using Pearson's chi-square test.

RESULTS

Out of 646 serum samples, 94 (14.6%) were positive and 552 (85.4%) were negative for anti-MICA antibodies. Patients with anti-MICA antibody had a graft survival 89.3% as compared to 94.7% in patients without anti-MICA antibody (P < 0.05). The hazard ratio for all patients was 3.0701 (P < 0.05). Out of the 340 patients with no HLA antibodies, the presence of anti-MICA antibodies without any HLA antibodies (n = 43) was associated with poor outcome in the patients (hazard ratio of 2.768, P < 0.05). The presence of MICA antibodies with HLA antibodies did not decrease the graft survival (hazards ratio of 1.3750, P > 0.05).

CONCLUSION

Preformed MICA antibodies independently increase the risk of kidney rejection and therefore recommend that guidelines should be formed for mandatory testing of these antibodies prior to renal transplant.

Soluble Major Histocompatibility Complex Class I related Chain A (sMICA) levels influence graft outcome following Renal Transplantation

BACKGROUND

Since soluble isoforms of MICA play an important role in modulating the immune response, we evaluated a possible correlation between their levels and development of acute rejection following renal transplantation.

METHODS

Serum samples collected at pre- and different time points post-transplant from 137 live related donor renal transplant recipients were evaluated retrospectively for sMICA levels and for the presence of MICA antibodies. Samples from 30 healthy volunteers were also tested as controls.

RESULTS

Significantly higher levels of sMICA were observed in the pretransplant sera of allograft recipients as compared to healthy controls. Patients with acute cellular rejection experienced a significant fall in their levels at the time of diagnosis as compared to their pretransplant values and posttransplant follow up time points (p = .01, .003, .005 and .04 respectively at pre vs biopsy (Bx), POD7 vs Bx, POD 30 vs Bx, POD 90 vs Bx). However, no such difference was noted in patients undergoing antibody mediated rejection. Further the study did not reveal any correlation on the presence/absence of MICA antibodies with either an increase or decrease in sMICA levels.

CONCLUSIONS

Estimating circulating levels of soluble MICA could provide useful information of prognostic importance in assessing graft outcome following renal transplantation.

Major Histocompatibility Complex Class I Chain-Related A (MICA) Molecules: Relevance in Solid Organ Transplantation

An ever growing number of reports on graft rejection and/or failure even with good HLA matches have highlighted an important role of non-HLA antigens in influencing allograft immunity. The list of non-HLA antigens that have been implicated in graft rejection in different types of organ transplantation has already grown long. Of these, the Major Histocompatibility Complex class I chain-related molecule A (MICA) is one of the most polymorphic and extensively studied non-HLA antigenic targets especially in the kidney transplantation. Humoral response to MICA antigens has repeatedly been associated with lower graft survival and an increased risk of acute and chronic rejection following kidney and liver transplantation with few studies showing conflicting results. Although there are clear indications of MICA antibodies being associated with adverse graft outcome, a definitive consensus on this relationship has not been arrived yet. Furthermore, only a few studies have dealt with the impact of MICA donor-specific antibodies as compared to those that are not donor specific on graft outcome. In addition to the membrane bound form, a soluble isoform of MICA (sMICA), which has the potential to engage the natural killer cell-activating receptor NKG2D resulting in endocytosis and degradation of receptor–ligand interaction complex leading to suppression of NKG2D-mediated host innate immunity, has been a subject of intense discussion. Most studies on sMICA have been directed toward understanding their influence on tumor growth, with limited literature focusing its role in transplant biology. Furthermore, a unique dimorphism (methionine to valine) at position 129 in the α2 domain categorizes MICA alleles into strong (MICA-129 met) and weak (MICA-129 val) binders of NKG2D receptor depending on whether they have methionine or valine at this position. Although the implications of MICA 129 dimorphism have been highlighted in hematopoietic stem cell transplantation, its role in solid organ transplantation is yet to be explored. This review summarizes the currently available information on MICA antibodies, soluble MICA, and MICA-129 dimorphism in a setting of solid organ transplantation.

MICA and NKG2D: Is There an Impact on Kidney Transplant Outcome?

This paper aims to present an overview of MICA and natural killer group 2 member D (NKG2D) genetic and functional interactions and their impact on kidney transplant outcome. Organ transplantation has gone from what can accurately be called a “clinical experiment” to a routine and reliable practice, which has proven to be clinically relevant, life-saving and cost-effective when compared with non-transplantation management strategies of both chronic and acute end-stage organ failures. The kidney is the most frequently transplanted organ in the world (transplant-observatory¹). The two treatment options for end-stage renal disease (ESRD) are dialysis and/or transplantation. Compared with dialysis, transplantation is associated with significant improvements in quality of life and overall longevity. A strong relationship exists between allograft loss and human leukocyte antigens (HLA) antibodies (Abs). HLA Abs are not the only factor involved in graft loss, as multiple studies have shown that non-HLA antigens are also involved, even when a patient has a good HLA matche and receives standard immunosuppressive therapy. A deeper understanding of other biomarkers is therefore important, as it is likely to lead to better monitoring (and consequent success) of organ transplants. The objective is to fill the void left by extensive reviews that do not often dive this deep into the importance of MICA and NKG2D in allograft acceptance and their partnership in the immune response. There are few papers that explore the relationship between these two protagonists when it comes to kidney transplantation. This is especially true for the role of NKG2D in kidney transplantation. These reasons give a special importance to this review, which aims to be a helpful tool in the hands of researchers in this field.

HLA-DRB and HLA-DQ genetic variability in patients with aspirin-exacerbated respiratory disease

BACKGROUND

Major histocompatibility complex (MHC) class II is involved in T-cell activation, cytokine secretion, and induction of immune responses. Cytokines, staphylococcus super antigens, and eosinophil activation are proposed to play important roles in aspirin-exacerbated respiratory disease (AERD).

OBJECTIVES

This study is aimed at investigating the association of HLA-DRB and DQ genetic variabilities in patients with AERD.

METHODS

A genetic association analysis in three different groups, including 33 patients with AERD, 17 patients with aspirin-tolerant asthma (ATA), and 100 healthy controls was performed. Oral aspirin challenge (OAC) test was performed to identify aspirin hypersensitivity. Pulmonary function test (PFT) was performed for all patients. Eosinophil percentage in nasal smear and peripheral blood and serum immunoglobin (Ig)E were investigated. HLA-DRB, HLA-DQA1, and HLA-DQB1 were genotyped using polymerase chain reaction.

RESULTS

HLA-DQB1*0302 (OR, 5.49, 95% confidence interval [CI],(2.40-12.59)), HLA-DQA1*0301 (OR, 2.90, 95% CI, (1.49-5.67)), HLA-DRB4 (OR, 2.94, 95% CI, (1.61-5.36)), and HLA-DRB1*04 (OR, 3.19, 95% CI, (1.57-6.47)) were higher in patients with AERD compared with controls. In patients with AERD, HLA-DQB1*0301 (OR,0.22, 95% CI, (0.09-0.54)), HLA-DQA1*0501 (OR, 0.42, 95% CI, (0.21-0.81)), HLA-DRB1*11 (OR, 0.30, 95% CI, (0.12-0.73)), and HLA-DRB3 (OR, 0.38, 95% CI, (0.21-0.70)) were significantly lower compared with healthy controls. Patients with AERD had lower frequencies of HLA-DQB1*0301 (OR, 0.27, 95% CI, (0.08-0.86)), and HLA-DRB1*011 (OR, 0.27, 95% CI, (0.08-0.86)) compared with ATA. Haplotypes of HLA-DRB1*04/ DQA1*0301/ DQB1*0302 (OR, 4.25, 95% CI, (1.94-9.29)) and HLA-DRB1*07 /DQA1*0201/ DQB1*0201 (OR, 3.52, 95% CI, (1.54-8.06)) were higher in patients with AERD compared with controls (all p < 0.05).

CONCLUSIONS

Results of this study suggest that HLA-DQB1*0302 and HLA-DRB1*04 and their related haplotypes are genes involved in predisposing patients to AERD, whereas HLA-DQB1*0301 and HLA-DRB1*011 have negative association with AERD.

Pre- and Posttransplant IgA Anti-Fab Antibodies to Predict Long-term Kidney Graft Survival

OBJECTIVES

Immunologic factors are reliable markers for allograft monitoring, because of their seminal role in rejection process. One of these factors is the immunoglobulin (Ig)A anti-Fab of the IgG antibody. This study aimed to evaluate the predictive value of pre- and posttransplant levels of this marker for kidney allograft function and survival.

METHODS

Sera samples of 59 living unrelated donor kidney recipients were collected before and after transplantation (days 7, 14, and 30) and investigated for IgA anti-Fab of IgG antibody levels using enzyme-linked immunosorbent assay in relation with allograft outcome.

RESULTS

Among 59 patients, 15 cases (25%) including 10 with acute rejection and 5 with chronic rejection episodes showed graft failure during a mean of 5 years of follow-up. High posttransplant levels of IgA anti-Fab antibodies were observed more frequently in patients with stable graft function (SGF) compared with patients with graft failure (P = 2 × 10(-6)). None of patients with acute or chronic rejection episodes had high levels of IgA anti-Fab antibodies at day 30 posttransplant compared with the SGF group (P = 10(-6) and P = .01, respectively). In addition, high levels of IgA anti-Fab antibody correlated with lesser concentration of serum creatinine at 1 month posttransplantation (P = .01). Five-year graft survival was associated with high levels of pre- and posttransplant IgA anti-Fab antibodies (P = .02 and P = .003, respectively).

CONCLUSIONS

Our findings indicate the protective effect of higher levels of IgA anti-Fab antibodies regarding to kidney allograft outcomes and long-term graft survival.

Pretransplant IgG reactivity to apoptotic cells correlates with late kidney allograft loss

Preexisting serum antibodies have long been associated with graft loss in transplant recipients. While most studies have focused on HLA-specific antibodies, the contribution of non-HLA-reactive antibodies has been largely overlooked. We have recently characterized mAbs secreted by B cell clones derived from kidney allograft recipients with rejection that bind to apoptotic cells. Here, we assessed the presence of such antibodies in pretransplant serum from 300 kidney transplant recipients and examined their contribution to the graft outcomes. Kaplan-Meier survival analysis revealed that patients with high pretransplant IgG reactivity to apoptotic cells had a significantly increased rate of late graft loss. The effect was only apparent after approximately 1 year posttransplant. Moreover, the association between pretransplant IgG reactivity to apoptotic cells and graft loss was still significant after excluding patients with high reactivity to HLA. This reactivity was almost exclusively mediated by IgG1 and IgG3 with complement fixing and activating properties. Overall, our findings support the view that IgG reactive to apoptotic cells contribute to presensitization. Taking these antibodies into consideration alongside anti-HLA antibodies during candidate evaluation would likely improve the transplant risk assessment.

Biomarkers of pulmonary rejection

Immunologic complications after lung transplantation (LT) include acute cellular rejection (ACR), antibody-mediated rejection (AMR), and most forms of chronic allograft dysfunction (CAD). ACR is an inflammatory process in which the reaction is mediated by the T-cell population. Most episodes of ACR fully recover with treatment, but repeated bouts are considered to be a risk factor for CAD. Biomarker cytokines interleukin (IL)-10, IL-15, IL-6, CCL5, CCR2 and IFNγ may play significant roles in this complication. Formerly bronchiolitis obliterans syndrome (BOS) or chronic rejection or most forms of CAD were considered to be immunologic complications not amenable therapeutic measures. CAD, the main limitation for long-term survival in LT, is characterized histologically by airway epithelial cell apoptosis and luminal fibrosis in the respiratory bronchioles causing airflow obstruction and, in some cases, lung parenchymal affectations causing restrictive lung disease. Several biomarkers have been studied in CAD, IL-6, IL-8, IL-17, IL-23, IL-13, IFN γ, and TGF β cytokines, pH, bile acid, and tripsine of gastroesophageal reflux and toll-like receptors of innate immunity. Herein we have reviewed the literature of biomarkers involved in lung rejection.

Expression of receptor activator of nuclear factor-kappa B ligand in leukocytes during acute kidney rejection after transplantation in rats

BACKGROUND

Acute cellular rejection of the transplanted kidney is an important cause of impaired graft function. One of the basic characteristics of acute cellular rejection according to the latest Banff classification of renal allograft pathology is the presence of a large number of T lymphocytes in the allografted tissue. Osteoprotegerin, receptor activator of nuclear factor-kappa B (RANK) and RANK ligand (RANKL), three relatively novel members of the tumor necrosis factor superfamily, have crucial roles not only in physiologic and pathologic bone metabolism but also in immunologic processes. The aim of our study was to determine the expression of RANKL and RANK by T lymphocytes and macrophages in acute cellular kidney allograft rejection in rats.

METHODS

The study included 15 male Wistar rats of 3 months old and 250-300 g as recipients and 15 male DA rats donors of 3 months old; and weight 250-300 g. When animals were sacrificed at 3 weeks to extract the transplanted kidney for pathohistologic analysis and immunoflorescence. all samples showed acute cellular rejection. Kidney sections were examined by dual-labeled immunofluorescence to detect CD4, CD8, or CD68 (red) and RANK or RANKL (green) with coexpressing cells as orange.

RESULTS

RANKL-positive expression colocalized with CD4(+) and CD8(+) T lymphocytes in acutely rejected kidney tissue. There was no association between CD4(+) and CD8(+) T cells with RANK expression, which was evident by infiltrating CD68-positive macrophages in the kidney tissue interstitium.

CONCLUSION

RANK and RANKL were expressed by T lymphocytes and macrophages in acute cellular kidney rejection after transplantation in rats.

[Complications during the hospitalization of kidney transplant recipients]

The objective of the study was to identify the complications in patients that have received a renal transplant. A Historical cohort performed in a university hospital from January/2007 through January/2009 with a sample of 179 patients; data collected retrospectively from the medical history of patients and submitted to statistical analyses. Mean age of patients was 43 (SD=13.7) years, 114 (63.7%) men, 95 (65.1%) non smokers and 118(66.93%) received the graft from a deceased donor. The main complications were rejection 68 (32.1%) and infection 62 (29.2%). There was statistical significance between rejection and median days of hospital stay (p < 0.001); days of use of central venous catheter (p = 0.010) and smoking status (p = 0.008); infection and central venous catheter (p = 0.029); median days of hospital stay (p < 0.001) and time of use of urinary catheter (p = 0.009). It was concluded that it is important to reduce the days of hospital stay and permanence of catheters, which may be considered in the planning of nursing care.

Early post-transplant immune monitoring can predict long-term kidney graft survival: soluble CD30 levels, anti-HLA antibodies and IgA-anti-Fab autoantibodies

This study aimed to investigate the predictive power of anti-HLA antibodies, sCD30 levels and IgA-anti-Fab autoantibody before and early after transplantation in relation to long-term kidney allograft survival. Pre- and post-transplant sera samples of 59 living-unrelated donor kidney recipients were tested for above risk factors by enzyme-linked immunoabsorbent assay. 15 out of 59 cases experienced rejection episodes (failure group). Pre- and post-transplant high sCD30 levels were significantly associated with graft failure (P=0.02 and P=0.004) and decreased 4 year graft survival (P = 0.009 and P = 0.001). Higher frequency of post-transplant HLA class-II antibody in the absence of class-I antibody was observed in failure group (P=0.007). Patients with post-transplant HLA class-I and class-II antibodies either alone or in combination showed significant lower 4 year graft survival. Recipients with high sCD30 levels in the presence of HLA class-I or class-II antibodies within 2 weeks post-transplant had poor graft survival (P = 0.004 and P = 0.002, respectively). High levels of post-transplant IgA-anti-Fab antibody was more frequent in functioning-graft patients (P = 0.00001), correlated with decreased serum creatinine levels (P = 0.01) and associated with improved graft survival (P = 0.008). Our findings indicate the deleterious effect of early post-transplant HLA antibodies and increased sCD30 levels dependently and protective effect of IgA-anti-Fab antibodies on long-term renal graft outcomes.

Harmful effect of preformed anti-MICA antibodies on renal allograft evolution in early posttransplantation period

BACKGROUND

Pretransplantation anti-major histocompatibility complex class I chain-related molecule A (MICA) sensitization is an uncommon event and its role on kidney graft evolution is not completely defined.

METHODS

A retrospective study of patients transplanted between 2005 and 2011 in our center (n=727) was performed. Recipients were classified in four groups, according either to multiplexed flow cytometry-recorded anti-human leukocyte antigen (HLA) and anti-MICA antibodies or to percent panel-reactive antibody (PRA; by complement-dependent cytotoxicity) and anti-MICA antibodies.

RESULTS

In the total cohort, 52 (7.15%) patients had preformed anti-MICA antibodies, and these were not related with anti-HLA, previous transplantations, or recipient female sex (potential pregnancies). Kaplan-Meier curves showed global allograft survival differences (P=0.042) mostly due to pronounced decrease in PRA+MICA+ group early after transplantation. Biopsy-proven allograft rejection rate increased after month 12 in PRA+MICA- group and was higher early after transplantation in PRA+MICA+ group (P=0.033). In paired comparisons, rejection incidence was superior in PRA+MICA- versus PRA-MICA- patients (17% vs. 7%; P=0.007) at 24 months, confirming the widely reported deleterious effect of PRA+ status, but at 3 months rejection was higher in PRA+MICA+ versus PRA-MICA- patients (14% vs. 2%; P=0.009). Among patients categorized according anti-HLA and anti-MICA antibodies, the most striking difference in rejection was observed at 3 months (8% in HLA-MICA+ vs. 2% in HLA-MICA- patients; P=0.032). In the multivariate analysis, HLA-MICA+ status at 3 months independently conferred the highest risk for rejection (odds ratio, 5.07; P=0.049).

CONCLUSIONS

Pretransplantation sensitization against MICA and HLA are independent events. Preformed anti-MICA antibodies independently increase risk for kidney rejection and enhance the deleterious effect of PRA+ status early after transplantation.

The effect of MICA antigens on kidney transplantation outcomes

Good HLA matches do not guarantee rejection-free kidney transplantation, indicating that other antigens might be targets for rejection. The major histocompatibility complex class I-related antigens A (MICA) are polymorphic. Mismatched MICA epitopes may lead to antibodies against MICA antigens and induce immune response. Establishment of detection technique for MICA, including solid-phase, immunofluorescence, flow-crossmatch, make it possible to detect the types of MICA antibodies. Therefore, the pathological role of MICA antibodies has received an increased attention in kidney transplantation. This review describes and summarizes the data from recent studies related to the impact of MICA antibodies on kidney allografts rejection and survival. And also provides evidence that the presence of MICA antibodies before or after transplantation, as a risk factor, is likely to be responsible for transplant outcomes.

Five-year clinical effects of donor bone marrow cells infusions in kidney allograft recipients: improved graft function and higher graft survival

Augmentation of microchimerism in solid organ transplant recipients by donor bone marrow cells (DBMC) infusion may promote immune hyporesponsiveness and consequently improve long-term allograft survival. Between March 2005 and July 2007, outcomes for 20 living unrelated donor (LURD) primary kidney recipients with concurrent DBMC infusion (an average of 2.19 ± 1.13 x 10⁹ donor cells consisting of 2.66 ± 1.70 x 10⁷ CD34⁺ cells) were prospectively compared with 20 non-infused control allograft recipients given similar conventional immunosuppressive regimens. With five years of clinical follow up, a total of 11 cases experienced rejection episodes (3 DBMI patients vs. 8 controls, p = 0.15). One DBMC-infused patient experienced chronic rejection vs. two episodes (1 biopsy-confirmed) in the control patients. Actuarial and death-censored 5-y graft survival was significantly higher in infused patients compared with controls (p = 0.01 and p = 0.03, respectively). Long-term graft survival was significantly associated with pre-transplant anti-HLA antibodies (p = 0.01), slightly with peripheral microchimerism (p = 0.09) and CD4⁺CD25⁺FoxP3⁺ T cells (p = 0.09). Immunosuppressant dosing was lower in infused patients than controls, particularly for mycophenolate mofetil (p = 0.001). The current findings as well as our previous reports on these patients indicates clinical improvement in long-term graft survival of renal transplant patients resulting from low-dose DBMC infusion given without induction therapy.

Consensus guidelines on the testing and clinical management issues associated with HLA and non-HLA antibodies in transplantation

BACKGROUND

The introduction of solid-phase immunoassay (SPI) technology for the detection and characterization of human leukocyte antigen (HLA) antibodies in transplantation while providing greater sensitivity than was obtainable by complement-dependent lymphocytotoxicity (CDC) assays has resulted in a new paradigm with respect to the interpretation of donor-specific antibodies (DSA). Although the SPI assay performed on the Luminex instrument (hereafter referred to as the Luminex assay), in particular, has permitted the detection of antibodies not detectable by CDC, the clinical significance of these antibodies is incompletely understood. Nevertheless, the detection of these antibodies has led to changes in the clinical management of sensitized patients. In addition, SPI testing raises technical issues that require resolution and careful consideration when interpreting antibody results.

METHODS

With this background, The Transplantation Society convened a group of laboratory and clinical experts in the field of transplantation to prepare a consensus report and make recommendations on the use of this new technology based on both published evidence and expert opinion. Three working groups were formed to address (a) the technical issues with respect to the use of this technology, (b) the interpretation of pretransplantation antibody testing in the context of various clinical settings and organ transplant types (kidney, heart, lung, liver, pancreas, intestinal, and islet cells), and (c) the application of antibody testing in the posttransplantation setting. The three groups were established in November 2011 and convened for a "Consensus Conference on Antibodies in Transplantation" in Rome, Italy, in May 2012. The deliberations of the three groups meeting independently and then together are the bases for this report.

RESULTS

A comprehensive list of recommendations was prepared by each group. A summary of the key recommendations follows. Technical Group: (a) SPI must be used for the detection of pretransplantation HLA antibodies in solid organ transplant recipients and, in particular, the use of the single-antigen bead assay to detect antibodies to HLA loci, such as Cw, DQA, DPA, and DPB, which are not readily detected by other methods. (b) The use of SPI for antibody detection should be supplemented with cell-based assays to examine the correlations between the two types of assays and to establish the likelihood of a positive crossmatch (XM). (c) There must be an awareness of the technical factors that can influence the results and their clinical interpretation when using the Luminex bead technology, such as variation in antigen density and the presence of denatured antigen on the beads. Pretransplantation Group: (a) Risk categories should be established based on the antibody and the XM results obtained. (b) DSA detected by CDC and a positive XM should be avoided due to their strong association with antibody-mediated rejection and graft loss. (c) A renal transplantation can be performed in the absence of a prospective XM if single-antigen bead screening for antibodies to all class I and II HLA loci is negative. This decision, however, needs to be taken in agreement with local clinical programs and the relevant regulatory bodies. (d) The presence of DSA HLA antibodies should be avoided in heart and lung transplantation and considered a risk factor for liver, intestinal, and islet cell transplantation. Posttransplantation Group: (a) High-risk patients (i.e., desensitized or DSA positive/XM negative) should be monitored by measurement of DSA and protocol biopsies in the first 3 months after transplantation. (b) Intermediate-risk patients (history of DSA but currently negative) should be monitored for DSA within the first month. If DSA is present, a biopsy should be performed. (c) Low-risk patients (nonsensitized first transplantation) should be screened for DSA at least once 3 to 12 months after transplantation. If DSA is detected, a biopsy should be performed. In all three categories, the recommendations for subsequent treatment are based on the biopsy results.

CONCLUSIONS

A comprehensive list of recommendations is provided covering the technical and pretransplantation and posttransplantation monitoring of HLA antibodies in solid organ transplantation. The recommendations are intended to provide state-of-the-art guidance in the use and clinical application of recently developed methods for HLA antibody detection when used in conjunction with traditional methods.