Cytotoxic T-lymphocyte antigen 4 gene polymorphisms and susceptibility to acute allograft rejection

Impact of CD 28, CD86, CTLA-4 and PD-1 genes polymorphisms on acute renal allograft rejection and graft survival among Egyptian recipients

To study the impact of four gene polymorphisms on acute renal allograft rejection (AR) and graft survival among Egyptian population. These 4 gene polymorphisms include: (1) CD 28 (rs3116496), (2) CD86 (rs1129055), (3) CTLA-4 (rs3087243), (4) PD-1 (rs2227982). This is a non-concurrent cohort study including 50 kidney transplant recipients diagnosed histopathologically as (AR) [study group] and another 50 matched allograft recipients without AR [control group]. Blood samples were taken from both groups and subjected to genotyping for the selected four genetic polymorphisms by TaqMan genotyping assay. The difference in genotypic distribution of CD 28: rs3116496 and CD86: rs1129055 wasn't statistically significant between the study and control groups (P = 0.22 and 0.33 respectively) and also both polymorphisms had no effect on graft survival (P = 0.36 and 0.74 respectively) while the addition of C allele to IVS3 +17T/C polymorphism in CD28 gene showed a protective effect against AR (P = 0.03). CTLA-4: rs3087243 AG genotype showed a protective effect against AR as it was more frequent in no rejection group compared to those with AR (P = 0.001) with a statistically significant impact on graft survival (P < 0.001), while PD-1: rs2227982 AG genotype was equally distributed between both groups (variant of unknown significance). There was no detected association between CD86 polymorphism: rs1129055 and CD 28 polymorphism: rs3116496 with the development of AR. However, C allele of CD 28 IVS3 +17T/C polymorphism and CTLA-4 polymorphism: rs3087243AG genotype both demonstrated a protective effect against AR.

Immunopathological insights into villitis of unknown etiology on the basis of transplant immunology

Villitis of unknown etiology (VUE) is an inflammatory disease characterized by the infiltration of maternal CD8 +T cells into the placental villi. Although the pathogenesis of VUE is still debated, dysregulation of the immune system appears to be an important factor in the development of the disease. Interaction of maternal T cells with the fetal antigens seems to be the trigger for the VUE onset. In this context, graft vs host disease (GVHD) and allographic rejection seem to share similarities in the VUE immunopathological mechanism, especially those related to immunoregulation. In this review, we compared the immunological characteristics of VUE with allograft rejection, and GVHD favoring a better knowledge of VUE pathogenesis that may contribute to VUE therapeutics strategies in the future.

Polymorphisms in CTLA-4 predict de novo donor specific antibody formation after kidney transplantation

The post-transplant development of donor-specific antibodies (DSAs) initiates the antibody-mediated rejection, which is associated with an increased rate of graft loss. Therefore, risk prediction of de novo DSA (dnDSA) is important for understanding long-term prognostic implications for kidney transplantation outcomes. Cytotoxic T lymphocyte antigen-4 (CTLA-4), a cell surface molecule, suppresses T cell responses. Single-nucleotide polymorphisms (SNPs) in CTLA-4 are known to be associated with acute rejection; however, their association with dnDSA formation is not established. In the present study, we investigated the impact of CTLA-4 SNPs on dnDSA formation after kidney transplantation (KT) by analyzing three CTLA-4 SNPs (rs231775, rs3087243, and rs5742909) in 88 recipients. Patients with the GG genotype of CTLA-4 SNPs rs231775 and rs3087243 had higher rates of dnDSA formation than patients with the AA genotype or heterozygous genotypes. In conclusion, our findings indicate that CTLA-4 SNPs are predisposing factors for dnDSA formation after KT.

Association of Polymorphisms in T-Cell Activation Costimulatory/Inhibitory Signal Genes With Allograft Kidney Rejection Risk

The genes CD28, CD86 and CTLA-4 conform the costimulatory (CD28-CD86) or inhibitory (CTLA-4-CD86) signal in T-cell activation. T-cell immune response has a critical role in allograft rejection, and single nucleotide polymorphisms (SNPs) located in these genes have been widely analyzed with controversial results. We analyzed a group of SNPs located in the three genes: CD28: rs3116496; CD86: rs1129055; and CTLA-4: rs231775 and rs3087243 in a cohort of 632 consecutively recruited kidney transplanted subjects. All polymorphisms were genotyped by TaqMan chemistry and the diagnosis of rejection was confirmed by biopsy and categorized according to the Banff classification. The analyses showed a statistically significant protective effect to T cell-mediated rejection (TCMR) in carriers of the CTLA-4 rs3087243*G allele, especially in patients with TCMR Banff ≥2 in the overall cohort and in patients without thymoglobulin induction therapy. Both associations were corroborated as independent factors in the multivariate analysis. Interestingly, associations with rejection were not found for any SNP in patients with thymoglobulin induction therapy. As expected, considering the major role of these genes in T-cell activation, no effect was observed for antibody-mediated rejection (ABMR). In conclusion, the SNP rs3087243 located in the CTLA-4 gene may be considered a useful independent biomarker for TCMR risk especially for severe TCMR in patients who did no received thymoglobulin induction therapy.

The Role of CTLA4 and Its Polymorphisms in Solid Organ and Haematopoietic Stem Cell Transplantation

HLA matching, transplantation technique, or underlying disease greatly influences the probability of long-term transplantation success. It has been hypothesised that genetic variation affecting antigen presentation also contributes to the outcomes of both solid organ transplantation and allogeneic haematopoietic stem cell transplantation (AHSCT). Those genes, along with those responsible for innate and adaptive immunity, have become targets of investigation. In this review, we focus on the role of CTLA4 in the process of acute graft rejection and summarise the progress in our understanding of its role in predicting the outcome. We present the results of the latest studies investigating the link between CTLA4 gene variability and AHSCT, as well as organ transplantation outcomes. While some studies found a link between +49 A/G and −318 C/T and transplantation outcomes, comprehensive meta-analyses have failed to present any association. The most recent field reviews suggest that the −1772 T/C (rs733618) CC genotype is weakly associated with a lower risk of acute graft rejection, while +49 A/G might be clinically meaningful when investigated in the context of combinations with other polymorphisms. Studies verifying associations between 12 CTLA4 gene SNPs and AHSCT outcomes present inexplicit results. Some of the most commonly studied polymorphisms in this context include +49 A/G (rs231775) and CT60 A/G (rs3087243). The results signify that, in order to understand the role of CTLA4 and its gene polymorphisms in transplantology, further studies must be conducted.

CTLA-4 rs231775 and risk of acute renal graft rejection: an updated meta-analysis with trial sequential analysis

Contrasting results exist on the association between CTLA-4 rs231775 and acute rejection in kidney transplant recipients. We herein conducted an updated systematic review with meta-analysis and trial sequential analysis (TSA) to clarify this relationship and to establish whether the current evidence is sufficient to draw firm conclusions. In addition, noteworthiness of significant pooled odds ratios (ORs) was estimated by false positive report probability (FPRP). A comprehensive search was performed through PubMed, Web of Knowledge, Cochrane Library and Open Grey up to October 2019. Fifteen independent cohorts, including a total of 5,401 kidney transplant recipients, were identified through the systematic review. Overall, no association was detected with the allelic (OR 1.07, 95% CI 0.88-1.30, P = 0.49), dominant (OR 0.94, 95% CI 0.73-1.22, P = 0.66) or the recessive (OR 1.18, 95% CI 0.97-1.43, P = 0.096) model of CTLA-4 rs231775. In each genetic model, the cumulative Z-curve in TSA crossed the futility boundary and entered the futility area. In addition, none of the significant genetic comparisons detected in the subsequent and sensitivity analyses or in previously reported meta-analyses were found to be noteworthy by FPRP. In conclusion, this study provides strong evidence that CTLA-4 rs231775 is not a clinically-relevant genetic risk determinant of acute rejection after renal transplantation.

A deeper understanding of the association between CTLA4 +49A/G and acute rejection in renal transplantation: an updated meta-analysis

To reevaluate the association between the costimulatory molecule cytotoxic T lymphocyte-associated antigen4 (CTLA4) single nucleotide polymorphism (SNP) +49A/G and acute rejection (AR) in renal transplantation, nine studies published before June 2013 were analyzed. Meta-analysis and cumulative meta-analysis (metacum) were performed for each genotype in a random/fixed effect model. The combined odds ratios (OR) with 95% confidence intervals (CI) were calculated to estimate the strength of the association. In the sensitivity analysis, a single study involved in the meta-analysis was deleted each time to investigate the influence of the individual data sets on the pooled ORs. Meta-analysis regression was used for some influence factors, such as year of publication, total number in each group (AR group and control group), ethnicity, the ratio of GG to GA + AA, the ratio of G to A in CTLA4 +49A/G. Overall, a significant correlation was noted between the CTLA4 SNP (+49A/G) and the risk of AR (for GG vs. AG + AA: OR = 1.35, 95% CI = 1.05-1.73, p = 0.02; for G vs. A: OR = 1.21, 95% CI = 1.03-1.42, p = 0.02), especially in the Asian subgroup (for GG vs. AG + AA: OR = 1.79, 95% CI = 1.15-2.78, p = 0.009; for G vs. A: OR = 1.47, 95% CI = 1.04-2.07, p = 0.03). Of the influence factors, the ratio of GG to GA+AA (p = 0.046) and the ratio of G to A (p = 0.017) were significant factors. In conclusion, our results suggest that CTLA4 +49A/G contribute to the risk of AR following renal transplantation.

Association of cytokine/costimulatory molecule polymorphism and allograft rejection: a comparative review

One reason for genetic variations among human individuals is SNP which may confer diverse disease susceptibility or resistance in a population. Genetic variations in a key immunoregulatory agent can manifest various immunological responses, such as graft rejection. In fact, the outcome of organ transplantation can be impacted by several genetic causes including polymorphisms in genes encoding cytokines and costimulatory molecules in the donor or recipient. Thus, it can be helpful to contemplate the SNPs relating to these immunological determinants in order to achieve an improved transplantation therapy.

HLA variants related to primary sclerosing cholangitis influence rejection after liver transplantation

AIM: To investigate influence of human leukocyte antigen (HLA) and killer immunoglobuline-like receptor (KIR) genotypes on risks of acute rejection (AR) after liver transplantation (LTX).

METHODS: In this retrospective study we included 143 adult donor-recipient pairs with a minimum of 6 mo follow-up after LTX for whom DNA was available from both donor and recipients. Clinical data, all early complications including episodes and severity of AR and graft/patient survival were registered. The diagnosis of AR was based on clinical, biochemical and histological criteria. All suspected episodes of AR were biopsy confirmed. Key classical HLA loci (HLA-A, HLA-B, HLA-C and HLA-DRB1) were genotyped using Sanger sequencing. 16 KIR genes were genotyped using a novel real time PCR approach which allows for determination of the diploid copy number of each KIR gene. Immunohistochemical staining for T (CD3), B (CD20) and natural killer (NK) cells (CD56 and CD57) were performed on liver biopsies from 3 different patient groups [primary sclerosing cholangitis (PSC), primary biliary cirrhosis and non-autoimmune liver disease], 10 in each group, with similar grade of AR.

RESULTS: Fourty-four (31%) patients were transplanted on the basis of PSC, 40% of them had AR vs 24% in the non-PSC group (P = 0.04). No significant impact of donor-recipient matching for HLA and KIR genotypes was detected. In the overall recipient population an increased risk of AR was detected for HLA-B*08 (P = 0.002, OR = 2.5; 95%CI: 1.4-4.6), HLA-C*07 (P = 0.001, OR = 2.4; 95%CI: 1.4-4.0) and HLA-DRB1*03 (P = 0.03, OR = 1.9; 95%CI: 1.0-3.3) and a decreased risk for HLA-DRB1*04 (P = 0.001, OR = 0.2; 95%CI: 0.1-0.5). For HLA-B*08, HLA-C*07 and DRB1*04 the associations remained evident in a subgroup analysis of non-PSC recipients (P = 0.04, P = 0.003 and P = 0.02, respectively). In PSC recipients corresponding P values were 0.002, 0.17 and 0.01 for HLA-B*08, HLA-C*07 and DRB1*04, respectively. A dosage effect of AR prevalence according to the PSC associated HLA alleles was also notable in the total recipient population. For HLA-B*08 the frequency of AR was 56% in HLA-B*08 homozygous recipients, 39% in heterozygous recipients and 21% in recipients lacking HLA-B*08 (P = 0.02). The same was observed for the HLA-C*07 allele with AR in 57%, 27% and 18% in recipients being homozygous, heterozygous and lacking HLA-C*07 respectively (P = 0.003). Immunohistochemical analysis showed similar infiltration of T, B and NK cells in biopsies with AR in all three groups.

CONCLUSION: We found significant associations between the PSC-associated HLA-B*08, HLA-C*07, HLA-DRB1*03 and HLA-DRB1*04 alleles and risk of AR in liver transplant recipients.

Recipient cytotoxic T lymphocyte antigen 4 +49 single-nucleotide polymorphism is not associated with acute rejection after liver transplantation in Chinese population

OBJECTIVE

Single-nucleotide polymorphisms (SNPs) in Cytotoxic T lymphocyte antigen 4 (CTLA-4) gene have been detected and proved to associate with the incidence of rejection after transplantation. However, previous studies gained inconsistent results about the association between CTLA-4 +49 single-nucleotide polymorphism and susceptibility of allograft rejection. Therefore we sought to clarify whether CTLA-4 +49 SNP influences the incidence of acute rejection after liver transplantation in Chinese population.

METHODS

Genomic DNA from 335 liver transplant recipients was genotyped for CTLA-4 +49 SNP by DNA sequencing. Acute rejection was confirmed by pathologic evidences. The association between CTLA-4 +49 SNP and incidence of acute rejection was then analyzed by dominant, recessive, codominant and overdominant models.

RESULTS

The incidence of acute rejection within the first 3 months was 11.9%. In acute rejectors, the frequency was 45% for G/G, 10% for A/A and 45% for A/G respectively, compared with 47.5% for G/G, 10.8% for A/A and 41.7% for A/G in non-acute rejectors. And no significant difference of allele distribution between these 2 groups was detected.

CONCLUSIONS

This study suggests that CTLA-4 +49 SNP is not associated with acute rejection after liver transplantation in Chinese population.

Genetic Predisposition and Renal Allograft Failure

Renal allograft rejection or dysfunction often results in graft failure, and remains the major obstacle in the success of renal transplantation. Various immunological and nonimmunological factors are involved in allograft rejection. In addition to human leukocyte antigen loci, several genetically controlled molecules have been identified in recent years as playing important roles in the process of rejection. Genetic variants in genes encoding different T-helper (Th) type 1 and Th2 cytokines, chemokines and their receptors, growth factors, molecules of the renin-angiotensin system, enzymes of the homocysteine pathway, and proteins acting as substrates of immunosuppressive drugs impact on the success of engraftment and highlight the concept of genetic predisposition to allograft rejection. This review evaluates specific genetic variants and their functional roles in graft failure, with an emphasis on the latest methodologies available for genotyping, and appropriate strategies to enable them to become a tool of predictive and individualized medicine to ensure better transplant outcome.

Polymorphisms in the cytotoxic T-lymphocyte antigen 4 gene and acute rejection risk in transplant recipients

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) gene polymorphisms have been reported to influence the risk for acute rejection (AR) in transplant recipients. However, the results still remain controversial and ambiguous. The objective of the current study was to conduct a meta-analysis investigating the association between polymorphisms in the CTLA-4 gene and the risk of AR in transplant recipients. Electronic searches for all publications were conducted on associations between this variant and acute rejection in Medline and Embase databases through November 2011. Crude odds ratios (ORs) with 95 % confidence intervals (CIs) were calculated to estimate the strength of the association. Three polymorphisms (+49 adenine/guanine [+49A/G], -318 cytosine/thymine [-318C/T], and the +6230G/A polymorphism [CT60]) in 18 case-control studies from ten articles were analyzed. This meta-analysis included 2,081 cases of transplant recipients in which 813 cases developed AR and 1,268 cases did not develop AR. The results indicated that there was no statistically significant association between the risk of AR and the +49A/G polymorphism or the -318C/T polymorphism (+49A/G: OR = 0.876, 95 % CI = 0.650-1.180 for GG vs. AA; OR = 1.121, 95 % CI = 0.911-1.379 for AG + GG vs. AA; -318C/T: OR = 0.397, 95 % CI = 0.138-1.143 for TT vs. CC; OR = 0.987, 95 %CI = 0.553-1.760 for CT + TT vs. CC). However, individuals who carried CT60 A allele might have a decreased risk of AR (AA vs. GG OR = 0.535, 95 % CI = 0.340-0.841, A vs. G OR = 0.759, 95 % CI = 0.612-0.914) in liver transplant recipients among Europeans, but because only two studies were included, so the result should be caution. In further stratified analyses for the +49A/G and the -318C/T polymorphisms, no obvious significant associations were found in subgroups of renal transplant recipients and Europeans, a reduced incidence of acute rejection was observed in liver transplant recipients that are homogenous for +49G (OR = 0.638, 95 % CI = 0.427-0.954 for GG vs. AA/AG), while this has not been observed in renal transplant recipients. Overall this meta-analysis suggests that +49A/G and the -318C/T polymorphisms in CTLA-4 may be not associated with the risk of rejection after organ transplantation, but CTLA +49A/G and +6230G/A polymorphisms may be associated with acute rejection after liver transplantation, not after renal transplantation. In future, more studies should be included to evaluate the association between +6230G/A polymorphism and AR risk.

Polymorphisms in cytotoxic T lymphocyte associated antigen-4 influence the rate of acute rejection after renal transplantation in 167 Chinese recipients

Gene polymorphisms of cytotoxic T lymphocyte associated antigen 4 (CTLA4) play an influential role in the graft rejection and long-term clinical outcome of organ transplantation. We investigated the associations of five CTLA4 single nucleotide polymorphisms (SNPs) (rs733618T/C, rs4553808A/G, rs5742909C/T, rs231775G/A, rs3087243G/A) on the early acute rejection (AR) of Chinese deceased donor renal transplantation recipients. Genotyping of the CTLA4 SNPs was performed in 167 deceased donor renal transplantation recipients. Each patient underwent a 6-month follow-up observation for AR. The incidence of AR during the 6 months post-transplantation was 26.9% (45 out of 167 patients). Patients experiencing AR were found to have a higher frequency of the rs733618TT genotype and T allele (p=0.000 and p=0.002, respectively). While the haplotype CACAG was merely observed in non-AR group (corrected p=0.000), the frequency of haplotype TACGG was significantly higher in AR group than in non-AR group even after 50,000 permutation tests (corrected p=0.018). In conclusion, these polymorphisms statistically significantly associated with acute renal allograft rejection may be considered as a risk factor of AR in Chinese renal transplantation recipients except for haplotype CACAG as a protective one.

(AT) repeat in the 3' untranslated region of the CTLA-4 gene and susceptibility to acute allograft rejection in Tunisian renal transplantation

Allograft rejection is an immune response relying on the proliferation and the differentiation of T cells. CTLA-4 is a co-stimulatory molecule, expressed on activated T lymphocytes, which has been shown to play a crucial role in the down-regulation of T-cell activation. Herein, we have examined the impart of a genetic marker in the CTLA-4 gene on renal transplant outcomes. A cohort of 144 renal recipients and 100 healthy subjects were genotyped by the fragments analysis method using an automated sequencer. Patients were classified into two groups: Group I included 31 HLA-identical haplotype allograft recipients and Group II, 113 showing one or more HLA haplotype mismatches. Forty patients (27.78%) developed at least one acute rejection episode (ARE): 9 in Group I and 31 in Group II. Before transplantation, 20 patients were lymphocytotoxic antibodies (LCT) positive: 4 Group I, 2 of whom developed an ARE, and sixty in Group II, including 8 with an ARE. The occurrence of an ARE was associated with the presence of LCT before transplantation among the entire cohort of patients (P = .032) and among Group II (P = .037). The allelic frequencies of (AT)n polymorphism did not reveal significant differences between patients and controls. The most prevalent alleles were the 88 bp (51% in controls and 44.44% in patients) and the 106 bp (8% and 10.76%, respectively). We noticed an increase of the 120 bp allele frequency among patients who had undergone an ARE compared with those who did not display this complication (8.75% vs 3.85%). Likewise, among LCT-negative Group I, recipients the incidence of the 120 bp allele was higher in ARE than non-ARE patients. Although the differences were not statistically significant, we propose that the 120 bp allele of the CTLA-4 gene (AT)n microsatellite a predisposes to acute rejection episodes in renal transplantation.

Polymorphisms of the CTLA4 gene and kidney transplant rejection in Korean patients

Cytotoxic T-lymphocyte-associated protein 4 (CTLA4) is a member of the immunoglobulin superfamily. CTLA4, which binds to B7 molecules on antigen- presenting cells, is expressed on activated T cells, thereby delivering negative signals that down-regulate T-cell proliferation and cytokine production. Consequently, CTLA4 may be a good candidate gene to evaluate in kidney transplantation rejection. In this study, we investigated whether polymorphisms of the CTLA4 gene were associated with susceptibility to kidney transplantation rejection. We genotyped three selected SNPs in the CTLA4 gene using direct sequencing in 325 renal transplant recipients. Of the SNPs examined, one (rs231775) showed a statistical association with late acute rejection (p=0.026, odds ratio (OR)=0.48, 95% confidence interval (CI)=0.23-0.93 in the dominant model). Also, the frequency of the G allele (rs231775) was higher in late acute rejection patients (p=0.013, OR=2.02, 95% CI=1.15-3.52). One CTLA4 gene polymorphism was associated with susceptibility to late acute rejection in kidney transplantation in Korean patients.

The influence of CTLA-4 gene polymorphism on long-term kidney allograft function in Caucasian recipients

The aim of the study was to examine whether CTLA-4 (CD152) and CD28 gene polymorphisms affect the outcome of kidney transplantation (KTx). Polymorphisms of the CTLA-4 gene (-318 C>T, +49 A>G, and the microsatellite polymorphism in the 3'UTR of exon 4 (AT)(n)) and a CD28 gene (IVS3 +17T>C) were investigated in 314 allograft recipients with a mean age of 41.9+/-12 years. The median time since KTx was 97.5 months. The genotypes of the SNPs were determined by SSP-PCR and (AT)(n) genotype by PCR and capillary electrophoresis (ABI Prism 310). In general, no relationship was found between the allele variants and acute rejection or graft function. Univariate and multivariate analyses showed no influence of CTLA-4 or CD28 polymorphism on graft/patient survival. In the individuals bearing the combination of the homozygous variant of low AT repeat number (82 bp) and the homozygous variant A (adenine) in CTLA-4 +49 A>G, higher eGFR was observed at one year after KTx, which was also maintained at 10 years. In summary, 24.2% of the studied patients carrying the "favorable" CTLA-4 genotype exhibited significantly higher allograft function than the 16.9% recipients with the "unfavorable" genotype up to 10 years post transplantation.

CTLA4 -1661A/G and 3'UTR long repeat polymorphisms are associated with ulcerative colitis and influence CTLA4 mRNA and protein expression

Reduced cytotoxic T-lymphocyte antigen 4 (CTLA4) expression has been proposed as a risk for autoimmunity. CTLA4 polymorphisms have been associated with several autoimmune diseases, including ulcerative colitis (UC). In this study, we performed genotyping for CTLA4 -1661A/G, -1722T/C and 3' untranslated region (AT)n repeat polymorphisms in 300 Chinese UC patients and in 700 healthy controls, and evaluated the effects of polymorphisms on full-length (flCTLA4) and soluble CTLA4 (sCTLA4) expression in UC patients. The frequency of the -1661G allele was higher in UC patients than in healthy controls (16.5 vs 11.4%, P=0.003, odds ratio (OR)=1.53, 95% confidence interval (95% CI): 1.17-2.01). The prevalence of (AT)n repeats of the CTLA4 gene carrying long alleles (≥116 bp) was more common in UC patients than in healthy controls (22.0 vs 6.3%, P<0.001, OR=4.21, 95% CI: 2.79-6.33), and was associated with extensive colitis (P=0.008). Among UC patients, long-allele carriers expressed lower levels of flCTLA4 and sCTLA4 mRNA and sCTLA4 protein than did short-allele carriers (P<0.001, P<0.001, P<0.001, respectively). CTLA4 gene -1661A/G and long 3' untranslated region (AT)n repeat polymorphisms are associated with UC in Central China. This is likely from decreased expressions of sCTLA4 mRNA and sCTLA4 protein. Our study suggests that CTLA4 has an important role in susceptibility for UC in Central China.

The immunological monitoring of kidney and liver transplants in adult and pediatric recipients

Over the last half century, kidney and liver transplantation have been recognized as the treatment of choice for adult and children with end-stage renal or liver failure. Infants present a relative naïve immune system, but they are capable of mounting both cellular and humoral immune responses to the foreign antigens presented by the allograft. Immune monitoring is a way of measuring functional and molecular correlates of immune reactivity which may provide clinically useful information for identifying patients who have an increase risk of acute rejection prior to clinical symptoms or develop transplant tolerance. However, although numerous assays have been shown to predict rejection, to date no assays have been demonstrated to detect or predict transplantation tolerance. This is a summary of the published literature on promising antigen-specific and non-antigen-specific assays used for immunological monitoring in solid organ transplantation. This work also attempts to review their applicability to pediatric transplantation, specifically, pediatric kidney and liver recipients.

Association of genetic variation in inducible costimulator gene with outcome of kidney transplantation

BACKGROUND

The closely-linked genes of CD28, cytotoxic T-lymphocyte associated antigen 4 (CTLA4), inducible costimulator (ICOS), and programmed cell death 1 on chromosome 2q encode costimulatory molecules, which are regulators of the T-cell activity. The T-cell mediated immune response has a major role in allograft rejection. Hence, the variation in these genes may have an effect on graft survival and the amount of immunosuppression needed, but so far the studies have restricted solely to the CTLA4 gene.

METHODS

We determined 13 single nucleotide polymorphisms in CD28, CTLA4, ICOS, and PPCD1 genes in 678 adult patients who received a kidney from deceased donor. The effect of genetic variation on the outcome of renal transplantation was analyzed.

RESULTS

Two markers on the ICOS gene, rs10183087 and rs4404254, were associated with delayed graft function (odds ratio=5.8; P=0.020 and odds ratio=5.8; P=0.019, respectively). Interestingly, the same ICOS variation has been shown to regulate the expression level of ICOS. We also demonstrated an association of the ICOS polymorphism rs10932037 with the graft survival (P=0.026).

CONCLUSIONS

The present results indicate that potentially functional genetic variation in T-cell costimulatory molecule ICOS has an effect on the outcome of kidney transplantation.

The impact of immune gene polymorphisms in kidney and liver transplantation

Since the completion of the Human Genome Project, it has become clear that genetic variation exists among individuals that can affect functional gene expression. This finding raises the possibility that differences in genetic phenotypes may account for the interindividual responses seen in the context of the alloimmune response. This review highlights studies examining the relative role of immunologic gene polymorphism in the context of renal and liver transplant outcomes (eg, acute rejection and graft survival). Furthermore, it examines the limitations and pitfalls in the study designs and concludes with the potential of single nucleotide polymorphism analysis in the future care of transplant recipients.

Genetic polymorphisms and the fate of the transplanted organ

There has been an abundance of publications describing genetic variability in molecules affecting innate and adaptive immunity, pharmacogenetics, and other nonimmunological factors like the renin-angiotensin aldosterone system, coagulation, and fibrosis markers. Studies indicated some associations between polymorphisms in these candidate genes with outcomes in organ transplantation and underlined a potential role of genetic variability in transplantation. To be clinically applicable, large prospective studies must be performed to better define the potential benefits of genotyping on these genetic markers and clinical outcomes. The purposes of this review are to summarize recent data describing associations of polymorphisms in both immunological and nonimmunological molecules with transplant outcomes, with a particular emphasis on renal transplantation, and discuss limitations and clinical implications.

Risk of adverse post-transplant events after kidney allograft transplantation as predicted by CTLA-4 +49 and TNF-α −308 single nucleotide polymorphisms: A preliminary study

Genetic differences between donor and recipient HLA haplotypes are of major importance for transplant rejection. Other genetic variations occurring in genes encoding cytokines and costimulatory molecules also appear to exert an influence on the manner the host immune system recognizes the allograft. The aims of this work were: 1) to study selected single nucleotide polymorphisms (SNPs) at the loci encoding the T-cell regulatory molecule CTLA-4 (CD152), and the cytokines interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-10, and transforming growth factor (TGF)-beta1 in a sample of healthy volunteers and a group of kidney-transplanted patients; and 2) to investigate whether an association exists between any of the SNPs studied and acute or chronic rejection, or non-responsiveness to steroid treatment during episodes of acute rejection (AR) after kidney allograft transplantation. When healthy volunteers were compared with transplanted patients, no significant differences were found in the distribution of genetic frequencies for any of the SNPs analyzed. However, in transplanted patients who received a kidney from a living related donor (KdTxL), a statistically significant association was found between carrying the CTLA-4 +49 A/A genotype and protection from experiencing acute rejection. No such association was found in the group of transplanted patients who received a kidney from a cadaveric non-related donor (KdTxCad). In both, KdTxL and KdTxCad patients, responsiveness to steroid treatment during acute rejection was also in association with the CTLA-4 (+49A/G) SNP. The CTLA-4 +49G allele was found at a very low frequency among steroid-resistant compared with steroid-sensitive patients. Finally, a statistically significant association was found between the presence of the TNF-alpha -308A allele and protection to suffer from chronic rejection. The genetic differences found may serve as risk predictors of adverse post-transplant events.

CTLA-4 Exon 1 (+49) and Promoter (−318) Gene Polymorphisms in Kidney Transplantation

To investigate the association between kidney transplant rejection and the polymorphisms of CTLA-4 gene exon 1(+49) and promoter (-318), genomic DNA of 70 renal transplant recipients and 110 healthy blood donors were genotyped by PCR-RFLP and PCR-SSP, respectively. The patients were classified in two groups: G1 included 33 HLA-identical recipients and G2, 37 one haplo-identical recipients. Thirty-one recipients experienced an acute rejection episode: 10 in G1 and 21 in G2. Ten G2 patients developed chronic allograft dysfunction (CAD). Allelic frequencies and genotype distribution were similar among patients and controls. CTLA-4 exon 1 genotype A/A and CTLA-4 promoter genotype C/C were significantly higher among G2 patients with CAD than without CAD (P < .01). The distribution of CTLA-4 exon 1-promoter genes did not reach significance between graft recipients and controls. The genotype frequency of (G/G-C/C) was increased among controls (42.72%) compared with graft recipients (G1 and G2; 35.71%). CTLA-4 polymorphisms gene were associated with susceptibility to chronic allograft dysfunction.

Tolerance Assays: Measuring the Unknown

Distinguishing transplant recipients who will benefit from a reduction in, or even the withdrawal of, immunosuppression from those who require intensive, lifelong immunosuppression will be dependent on developing strategies for immune monitoring. Currently, no assays have been shown to accurately predict the development or presence of donor-specific tolerance in humans after transplantation. In this overview we describe and discuss those assays that we believe may be useful for identifying tolerant transplant recipients. Validation of "tolerance" assays will be critical for the safe development of tolerance regimens in humans.

Study of Fas (CD95) and FasL (CD178) polymorphisms in liver transplant recipients

The Fas receptor is capable of transducing apoptotic cell death upon interaction with their ligand (FasL). Recent studies suggest that the Fas/FasL system is involved both in graft rejection and in transplantation tolerance. In this study, we analyzed the effect of Fas and FasL polymorphisms in liver allograft outcome. Fas and FasL polymorphisms were analyzed in 151 primary liver graft recipients. The Fas (-670 A/G) and the FasL (IVS2nt -124 A/G and IVS3nt 169 T/delT) polymorphisms were analyzed by polymerase chain reaction-restriction fragment length polymorphism. Fas -1377 G/A polymorphism was determined by allele-specific amplification. Fas and FasL polymorphisms were not associated with acute and chronic rejection in liver transplant. In contrast, those recipients bearing the AA -670 Fas genotype showed significantly lower graft survival rate (S = 40%) than those bearing the GA genotype (S = 63.1%). These differences were detected from the first year post-transplant. Multivariate analysis confirmed that the AA genotype increased the risk of liver graft loss. This work suggests for the first time a possible harmful effect of Fas -670 AA genotype on liver graft survival, whereas the Fas and FasL polymorphisms are not associated with acute or chronic rejection in liver graft recipients.

Possible Association of Cytotoxic T-Lymphocyte Antigen 4 Gene Promoter Single Nucleotide Polymorphism With Acute Rejection of Allogeneic Kidney Transplant

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) molecule is an important inhibitor of T-lymphocyte response. Polymorphisms in the CTLA-4 gene have been described to be associated with numerous autoimmune diseases. However, similar studies in solid organ transplantation have been scarce. Therefore, we examined the distribution of three single nucleotide dimorphisms, namely, -1147T/C, -318C/T, and +49A/G, in two groups of allogeneic kidney graft recipients: (1) those with at least one acute rejection episode ("rejectors"; n = 38) and (2) those with no signs of acute rejection ("nonrejectors"; n = 53). Allele frequencies in both groups of patients were similar in two positions, -1147T/C and +49A/G. However, rejectors showed slight differences from nonrejectors for allele and genotype frequencies in position -318. The -318T allele was two times less frequent among rejectors than nonrejectors, a difference that was close to statistical significance (P = .039; P corrected = .0583), and may reach it when greater numbers of patients are tested.

Immune Response Gene Polymorphisms in Renal Transplant Recipients

BACKGROUND

T-cell activation and regulation are under genetic control and vary between individuals. However, the influence of functional immune response gene polymorphisms on transplant outcomes remains controversial.

METHODS

A case-control design compared 100 white renal transplant recipients with or without acute graft rejection during the first year posttransplant and 50 normal controls. The polymorphic frequencies of the T-cell signaling genes CD45, CD40L and CTLA-4, and the cytokine genes TNF-alpha, IFN-gamma, IL-10 and TGF-beta1 were studied. The primary analysis examined rejection risk, and subsidiary analyses graft failure and patient death.

RESULTS

Multivariate analysis showed no significant association between acute rejection and single nucleotide polymorphisms in CTLA-4, TGF-beta1, IL-10 or TNF-alpha genes or dinucleotide repeat polymorphisms in IFN-gamma and CD40L genes. Allele CD40L-147 was associated with reduced graft failure (P=0.004), and TGFb-25pro with increased graft failure (P=0.0007), although the latter showed a bidirectional dose effect. There was no significant association between patient death and any polymorphisms in the genes examined. The variant (G) allele of the CD45 gene was not detected in the study population. Minor differences in carriage rates observed by univariate analysis did not predict graft or patient outcome in multivariate analysis.

CONCLUSION

The primary analysis demonstrated no significant association between the immune response gene polymorphisms examined and acute renal graft rejection in Caucasian patients receiving triple immunosuppression. Subsidiary analyses suggesting an influence of CD40L and TGFbeta1 genes on graft survival require independent confirmation.

Interleukin-10 production genotype protects against acute persistent rejection after lung transplantation

BACKGROUND

Our previous studies demonstrated that cytokine gene polymorphisms are related to acute rejection in pediatric heart transplantation; a decreased tumor necrosis factor (TNF)-alpha production genotype combined with an increased or intermediate interleukin (IL)-10 production genotype was associated with the smallest incidence of acute rejection. The objective of this study was to determine whether cytokine genotypes TNF-alpha, IL-10, IL-6, interferon-gamma, and transforming growth factor beta were associated with acute persistent rejection after lung transplantation.

METHODS

Cytokine genotyping was performed in 119 adult lung transplantation recipients who underwent surveillance transbronchial biopsies during their first year after transplantation. We categorized recipients with acute persistent rejection if they had 2 consecutive biopsy specimens at >/=Grade A2 despite anti-rejection treatment. We performed cytokine genotyping using the polymerase chain reaction-sequence specific primers technique, with a commercially available kit.

RESULTS

We analyzed the IL-10 genotype in 116 patients. For the increased IL-10 production genotype, 7 of 20 patients (35%) were persistent rejecters. In comparison, 57 of 96 patients (59%) with intermediate or decreased IL-10 production genotype had acute persistent rejection (p = 0.046). For IL-10 haplotypes associated with intermediate IL-10 production, 30 of 45 patients with GCC/ACC haplotype (67%) had acute persistent rejection compared with 10 of 22 patients with GCC/ATA (45%). In the patients with intermediate IL-10 production, 17 of 22 (77%) with IL-10 GCC/ACC and IL-6 G/C had acute persistent rejection, whereas only 2 of 7 patients (29%) with IL-10 GCC/ATA and IL-6 G/G had acute persistent rejection (p = 0.018).

CONCLUSIONS

In lung transplant recipients, the increased IL-10 production genotype protects against acute persistent rejection when compared with the intermediate or decreased IL-10 production genotypes. The intermediate IL-10 production genotype in lung transplant recipients can be differentiated into 2 haplotype responses, with the GCC/ACC haplotype associated more with acute persistent rejection. In lung transplant recipients, the immunomodulatory effects of IL-6 are differentiated in the G/C and G/G alleles in conjunction with IL-10 haplotypes, with G/C being associated with more acute persistent rejection in conjunction with the IL-10 GCC/ACC haplotype. Future pharmacogenomic models may incorporate these associations with acute persistent rejection in lung transplant recipients to formulate individualized therapeutic regimens.

Recipient ctla-4 +49 G/G genotype is associated with reduced incidence of acute rejection after liver transplantation

The aim of this pilot study was to investigate whether acute rejection after liver transplantation is associated with known single-nucleotide polymorphisms (SNPs) in the CD86- and CTLA-4 genes of liver-transplant donors and recipients. Single nucleotide polymorphisms were determined in 135 liver transplant recipients and in 73 donors. Acute rejection was not associated with CD86 + 1057 G/A genotype distributions in donors and in recipients. In univariate analysis recipient CTLA-4 -318 G/T and + 49 A/G genotype distributions were both weakly associated with acute rejection. Multivariate analysis revealed that the CTLA-4 + 49 SNP, but not the -318 SNP, was independently of other risk factors associated with acute rejection. Only one out of 13 CTLA-4 + 49 G-homozygotes (8%) experienced acute rejection(s) compared with 40% of A/A or A/G recipients. The CTLA-4 + 49 A/G SNP, which results in an amino acid substitution in the signal peptide of the protein, did not, however, affect intracellular expression or trafficking of CTLA-4 in T cells, nor soluble serum CTLA-4 concentrations of the liver transplant recipients. In conclusion, this pilot study suggests that liver transplant recipients homozygous for CTLA-4 + 49 G have a reduced risk of acute rejection.

The impact of costimulatory molecule gene polymorphisms on clinical outcomes in liver transplantation

CTLA-4 and CD28 deliver opposing signals for T-cell proliferation. We examined single nucleotide polymorphisms (SNPs) CTLA-4 -318C/T and CD28 IVS3 +17T/C for associations with acute rejection in liver transplant recipients. These and two other polymorphisms in CTLA-4 [microsatellite polymorphism +642(AT)n and SNP +49 A/G] were also analyzed for influence on graft survival. Two hundred and eleven liver transplant recipient genotypes were determined by direct sequencing or restriction fragment length polymorphism analysis of PCR-amplified genomic DNA. Mean graft survival for patients with the GG genotype of CTLA-4 +49 A/G was 58.5 +/- 6.0 months compared with 70.3 +/- 4.0 months and 73.8 +/- 2.8 months for the AA and AG genotypes, respectively (p = 0.0055). This is in support of previous studies suggesting decreased CTLA-4 function and increased incidence of autoimmune disease for this genotype. The 92-, 94-, and 100-bp alleles of CTLA-4 +642(AT)n occurred more often in African-American transplant recipients and were associated with decreased graft survival (p = 0.0001 and 0.007, respectively) but the independence of these variables could not be established. No associations with acute rejection or graft survival were found for CTLA-4 -318C/T or CD28 IVS3 +17T/C. The described associations between CTLA-4 gene polymorphisms and transplant outcomes provide the foundation for further investigations leading to genetic risk stratification for transplant recipients.

Genetic variability and transplantation

PURPOSE OF REVIEW

The purpose of this review is to summarize recent advances within the area of genetic polymorphisms with a specific emphasis on renal transplantation, and to discuss the potential clinical applications.

RECENT FINDINGS

Due to recent advances in molecular techniques, there has been an abundance of publications describing genetic variability in molecules relevant to transplant outcome. Many studies are now demonstrating associations between polymorphisms in these candidate genes and outcomes in organ transplantation.

SUMMARY

These studies emphasize the potential role of genetic variability in transplantation, and provide the rationale for large prospective studies to clearly define the potential benefits of genotyping in the risk stratification of transplant recipients.

The impact of polymorphisms in chemokine and chemokine receptors on outcomes in liver transplantation

Chemokines and their corresponding receptors likely play a central role in directing mononuclear cells to the graft sites during rejection. Genes for the chemokine stromal derived factor-1 (SDF1) and CC chemokine receptors CCR2 and CCR5 are characterized by polymorphisms which alter their function. We genotyped DNA of 207 liver transplant recipients by PCR or PCR-RFLP for CCR2-641, CCR5delta32, and SDF1-3'A polymorphisms, and examined their association on outcomes in liver allograft recipients. Due to the low number of patients homozygous for CCR2-641 and CCR5delta32, only the effects of their heterozygous variants were addressed in this study. None of the investigated polymorphisms showed a significant shift in gene frequency in acute rejection and rejection-free groups, or for graft survival. The gene frequency of the SDF1-3'A allele was significantly (p = 0.034) higher in patients who died (29.0%, n = 31) compared to recipients still alive (17.1%, n = 172). The mean patient survival time post transplant was 134 months in patients with SDF1 wild-type, significantly (log rank p = 0.014) longer than 98 months in patients with at least one SDF1-3'A allele. The CCR2 and CCR5 polymorphisms were not associated with significant differences in mortality rate. In conclusion, CCR2-641, CCR5delta32, and SDF1-3'A genotypes did not influence the risk for acute rejection or graft survival. However, in liver allograft recipients SDF1-3'A is significantly associated with higher mortality.

Gene polymorphisms and transplantation

The influence of gene polymorphisms in key immunoregulatory molecules on the clinical course post-transplant has become an area of active research, since it offers a possible explanation for the heterogeneity in outcomes between individuals. Several groups have now investigated the association of polymorphisms in molecules--including cytokines, cytokine receptors, adhesion molecules and costimulatory molecules--that participate in the immune response to an allograft. Several interesting observations have been made that would suggest that genetic variability influencing allograft survival reaches beyond that of the MHC molecules.