Effect of HLA-DR matching on acute rejection after clinical heart transplantation might be influenced by an IL-2 gene polymorphism

Association of the Number of HLA-DR Mismatches With Early Post-transplant Acute Cellular Rejection Among Heart Transplantation Recipients: A Cohort Study in Japanese Population

BACKGROUND

Although many risk factors are reported about graft rejection after heart transplantation (HTx), the effect of HLA mismatch (MM) still remains unknown, especially in the Japanese population. The aim of the present study was to investigate the influence of HLA MM on graft rejection among HTx recipients in Japan.

METHODS

We retrospectively investigated the association of the number of HLA MM including class I (A, B) and class II (DR) (for each locus MM: 0 to 2, total MM: 0 to 6) and the incidence of moderate to severe acute cellular rejection (ACR) confirmed by endomyocardial biopsy (International Society for Heart and Lung Transplantation grade ≥ 3A/2R) within 1 year after HTx.

RESULTS

Between 2007 and 2014, we had 49 HTx cases in our institute. After excluding those with insufficient data and positive donor-specific antigen, finally 35 patients were enrolled. Moderate to severe ACR was observed in 16 (45.7%) patients. The number of HLA-DR MM was significantly associated with the development of ACR (ACR+: 1.50 ± 0.63, ACR-: 1.11 ± 0.46, P = .029). From univariate analysis, DR MM = 2 was the only independent risk factor for ACR episodes (P = .017). The frequency of ACR within 1 year was significantly higher in those with DR MM = 2 (DR MM = 0 to 1: 0.3 ± 0.47, DR MM = 2: 1.17 ± 1.34 times, P = .007).

CONCLUSIONS

The number of HLA-DR MMs was associated with the development and recurrence of ACR episodes among HTx recipients within 1 year after transplantation in Japanese population.

Predictive Genomics of Adverse Events After Cardiac Surgery

Significant, yet highly individual, thrombotic and inflammatory responses to surgery provide an excellent opportunity for insight into the genomic impact upon a patient's postoperative course. Cardiac surgery elicits the most profound perioperative disturbance and is associated with the highest incidence of adverse outcomes of any elective surgical procedure. Thus, cardiac surgical patients are an ideal population in which to evaluate the influence of complex traits on perioperative morbidity and mortality. This review describes the application of fundamental genetics upon the occurrence of adverse outcomes after cardiac surgery and cardiac transplantation. Specific emphases include a brief primer of the principles of genetics concentrating on the effects of variation within the human genome upon clinical outcomes and the differences between so-called Mendelian traits and complex traits. Four important clinical diseases dealt with in this review as examples of the impact of genetic factors on clinical outcomes are the genetics of heparin-induced thrombocytopenia, heart transplantation rejection and vasculopathy, atrial fibrillation, and infection.

Clinical impact of cytokine and growth factor genetic polymorphisms in thoracic organ transplantation

Demographic and clinical risk factors may only partially predict short- and long-term outcomes after thoracic transplantation. The interindividual variability seen in rejection profiles could be related to the recipient's or donor's genetic background. Rejection, either acute or chronic, elicits an alloimmune response that involves a complex network of cytokines, growth factors, adhesion molecules, and other molecules, which may modulate the immune response toward rejection or, conversely, mediate graft acceptance. Herein, the authors discuss the current evidence regarding the importance of genetic polymorphisms as independent predictors of allograft outcome. They believe that pretransplant genotype profiling of patients, in combination with other relevant clinical information, might be useful to predict the risk for posttransplant adverse events and also to facilitate the implementation of individualized immunosuppression.

Immunoglobulin M-to-Immunoglobulin G Anti-Human Leukocyte Antigen Class II Antibody Switching in Cardiac Transplant Recipients Is Associated With an Increased Risk of Cellular Rejection and Coronary Artery Disease

Background— Activation of T cells induces immunoglobulin (Ig)M-to-IgG B-cell isotype switching via costimulatory regulatory pathways. Because rejection of transplanted organs is preceded by alloantigen-dependent T-cell activation, we investigated whether B-cell isotype switching could predict acute cellular rejection and the subsequent development of transplantation-related coronary artery disease (TCAD) in cardiac transplant recipients.

Methods and Results— Among 267 nonsensitized heart transplant recipients, switching from IgM to IgG anti-human leukocyte antigens (HLA) antibodies directed against class II but not against class I antigens was associated with a shorter duration to high-grade rejection, defined as International Society for Heart and Lung Transplantation grade 3A or higher ( P <0.001), a higher cumulative rejection frequency ( P =0.002), accelerated development of TCAD ( P =0.04), and decreased late survival ( P =0.03). Conversely, the persistence of IgM anti-HLA antibodies against class II but not against class I antigens for >30 days and the lack of IgG isotype switching were associated with protection against both acute rejection ( P =0.02) and TCAD ( P =0.05). Alloisotype switching coincided with T-cell activation, as evidenced by increased serum levels of soluble CD40 ligand costimulatory molecules. Finally, a case-control study showed that reduction of cardiac allograft rejection by mycophenolic acid was accompanied by reduced CD40 ligand serum levels and the prevention of IgM-to-IgG anti-HLA class II antibody switching.

Conclusions— T-cell-dependent B-cell isotype switching and the consequent production of IgG anti-HLA class II antibodies are strongly correlated with acute cellular rejection, a high incidence of recurrent rejections, TCAD, and poor long-term survival. Detecting this isotype switch is a clinically useful surrogate marker for in vivo T-cell activation and may provide a noninvasive approach for monitoring the efficacy of T-cell targeted immunosuppressive therapy in heart transplant recipients.

Confirmation of QTL on porcine chromosomes 1 and 8 influencing leukocyte numbers, haematological parameters and leukocyte function

A genome wide search in European Wild Boar x Swedish Yorkshire (W x Y) inter-cross pigs has earlier identified quantitative trait loci (QTL) for leucocyte number and function on porcine chromosomes 1 and 8 (SSC 1 and 8). To verify the involvement of these chromosomal regions in the regulation of haematocrit (Hem) and haemoglobin (Hb) levels, leucocyte numbers and in vitro leukocyte functions (mitogen induced proliferation and IL-2 production, virus induced interferon-alpha production and neutrophil phagocytosis), animals of different genetic backgrounds were analysed. The animals comprised a back-cross sire family (n=47) of W x Y pigs and six crossbred [Y x Landrace (L)] sire families (n=191). They were genotyped for 16 genetic markers and an interval analysis was performed. On SSC1, a QTL close to S0082 on the q-arm that influenced numbers of white blood cells in L x Y pigs and numbers of band neutrophils and CD8(+) cells in W x Y pigs was identified (P<or=0.01). An additional SSC1 QTL was identified on the p-arm close to S0008 with influence on numbers of CD2(+) cells in W x Y pigs (P<or=0.05). On SSC8, a QTL influencing Hb (P<or=0.01) and Hem (P<or=0.05) levels was identified close to KIT in the W x Y pigs. For L x Y pigs, a second QTL, distal to KIT and close to S0069, on SSC8 influenced the numbers of MHCII(+) cells and mitogen induced proliferation (P<or=0.05), whilst the QTL close to KIT influenced the number of IgM(+) cells in these pigs (P<or=0.05). The results confirm the involvement of earlier identified regions of SSC1 and SSC8 on porcine immune parameters and some candidate genes were suggested.

Interleukin-2 gene polymorphism is associated with renal but not cardiac transplant outcome

It was recently shown that IL-2 gene single nucleotide polymorphism (SNP) at position -330 (G-->T) is related to in vitro cytokine production levels, with the T/T and T/G genotypes being associated with low production and the G/G genotype associated with high production. The objective of this study was to investigate a possible influence of this polymorphism on renal and cardiac allograft outcomes. IL-2 SNP G-T (-330) was determined by PCR-RFLP in 67 recipients of heart allografts and in 63 recipients of renal grafts from HLA-haplo-identical, related donors. A higher frequency of the T/T genotype was observed in renal transplant patients who experienced at least one acute rejection episode during the first 3 months after transplantation than in those without rejection during this period (80% vs 49%, respectively, P <.05). Accordingly, the same genotype tended to be more frequent in renal recipients with a 6-month serum creatinine level above 1.5 mg/dL (median value for the whole group of kidney recipients) than in patients with lower creatinine levels (79% vs 45%, P <.08). Regarding cardiac transplant recipients, no associations were observed concerning acute rejection or graft survival. The finding of the association of T/T but not T/G genotype with acute kidney rejection was unexpected considering that both genotypes were shown to be associated with equal (low) IL-2 in vitro production. Further studies are necessary not only to dissect the nature of IL-2 T/T genotype association with kidney rejection, but also to explain why this genotype does not apparently influence cardiac allograft outcome.

Recipient gene polymorphisms in the Th-1 cytokines IL-2 and IFN-gamma in relation to acute rejection and graft vascular disease after clinical heart transplantation

IL-2 and IFN-gamma are associated with acute rejection (AR) and graft vascular disease (GVD) after clinical heart transplantation. Polymorphisms in the genes of IL-2 (T-330G in the promoter) and IFN-gamma (CA repeat in the first intron) influence the production levels of these cytokines. Therefore, these polymorphisms might have an effect on the outcome after transplantation. To investigate possible effects of genetic variations in IL-2 and IFN-gamma genes on AR and GVD, we analyzed the IL-2 T-330G and the IFN-gamma CA repeat polymorphism in DNA of 301 heart transplant recipients. No associations were found for allele or genotype distributions between patients with or without AR (IL-2 allele frequency: P=0.44, genotype distribution: P=0.46; IFN-gamma allele frequency P=0.10, genotype distribution 12 repeats allele: P=0.21). Also, no associations were found analyzing the number (0 vs. 1 vs. >or=1) of AR (IL-2 allele frequency: P=0.59; genotype distribution: P=0.37; IFN-gamma allele frequency: P=0.27, genotype distribution 12 repeats allele: P=0.41) or analyzing the polymorphisms in patients with AR within the first month or thereafter (IL-2 allele frequency: P=0.45, genotype distribution: P=0.38; IFN-gamma allele frequency: P=0.21, genotype distribution 12 repeats allele: P=0.41). Analyzing both polymorphisms in relation to GVD, resulted in comparable allele and genotype distributions (IL-2 allele frequency: P=0.75; genotype distribution: P=0.77; IFN-gamma allele frequency: P=0.70, genotype distribution 12 repeats allele: P=0.63). In conclusion, we did not detect an association between the IL-2 T-330G promoter polymorphism and CA repeat polymorphism in the first intron of the IFN-gamma gene and AR or GVD after heart transplantation.