Chemokine receptor polymorphism and risk of acute rejection in human renal transplantation

Donor and recipient chemokine receptor CCR5 genotype is associated with survival after bone marrow transplantation

Despite continual improvement, morbidity and mortality after hematopoietic stem cell transplantation (HSCT) remain high. The importance of chemokines in HSCT lies in their regulation of immune responses that determine transplantation outcomes. We investigated the role of recipient and donor chemokine system gene polymorphisms by using a candidate gene approach on the incidence of graft-versus-host disease and posttransplantation outcomes in 1370 extensively human leukocyte antigen-matched, unrelated donor-recipient pairs by using multivariate Cox regression models. Our analysis identified that recipients homozygous for a common CCR5 haplotype (H1/H1) had better disease-free survival (DFS; P = .005) and overall survival (P = .021). When the same genotype of both the donor and recipient were considered in the models, a highly significant association with DFS and overall survival was noted (P < .001 and P = .007, respectively) with absolute differences in survival of up to 20% seen between the groups at 3 years after transplantation (50% DFS for pairs with recipient CCR5 H1/H1 vs 30% for pairs with donor CCR5 H1/H1). This finding suggests that donor and/or recipient CCR5 genotypes may be associated with HSCT outcome and suggests new diagnostic and therapeutic strategies for optimizing therapy.

Perioperative genomic profiles using structure-specific oligonucleotide probes

OBJECTIVES

Many complications in the perioperative interval are associated with genetic susceptibilities that may be unknown in advance of surgery and anesthesia, including drug toxicity and inefficacy, thrombosis, prolonged neuromuscular blockade, organ failure and sepsis. The aims of this study were to design and validate the first genetic testing platform and panel designed for use in perioperative care, to establish allele frequencies in a target population, and to determine the number of mutant alleles per patient undergoing surgery. DESIGN/SETTING/PARTICIPANTS AND METHODS: One hundred fifty patients at Marshfield Clinic, Marshfield, Wisconsin, 100 patients at the Medical College of Wisconsin Zablocki Veteran's Administration Medical Center, Milwaukee, Wisconsin, and 200 patients at the University of Wisconsin Hospitals and Clinics, Madison, Wisconsin undergoing surgery and anesthesia were tested for 48 polymorphisms in 22 genes including ABC, BChE, ACE, CYP2C9, CYP2C19, CYP2D6, CYP3A4, CYP3A5, beta2AR, TPMT, F2, F5, F7, MTHFR, TNFalpha, TNFbeta, CCR5, ApoE, HBB, MYH7, ABO and Gender (PRKY, PFKFB1). Using structure-specific cleavage of oligonucleotide probes (Invader, Third Wave Technologies, Inc., Madison, WI), 96-well plates were configured so that each well contained reagents for detection of both the wild type and mutant alleles at each locus.

RESULTS

There were 21,600 genotypes confirmed in duplicate. After withdrawal of polymorphisms in non-pathogenic genes (i.e., the ABO blood group and gender-specific alleles), 376 of 450 patients were found to be homozygous for mutant alleles at one or more loci. Modes of two mutant homozygous loci and 10 mutant alleles in aggregate (i.e., the sum of homozygous and heterozygous mutant polymorphisms) were observed per patient.

CONCLUSIONS

Significant genetic heterogeneity that may not be accounted for by taking a family medical history, or by obtaining routine laboratory test results, is present in most patients presenting for surgery and may be detected using a newly developed genotyping platform.

Genetic interactions between the donor and the recipient for susceptibility to acute rejection in kidney transplantation: polymorphisms of CCR5

BACKGROUND

Acute rejection (AR) contributes to the development of chronic allograft nephropathy that is the major cause of graft failure. We analyzed the 59029G>A polymorphism and an internal 32 bp deletion (CCR5 32) of CCR chemokine receptor 5 (CCR5) Delta and tried to prove the hypothesis that genetic interactions between the donor and the recipient influence the development of AR.

METHODS

We detected genetic polymorphisms by the TaqMan(R) method and by sizing PCR amplicons (n = 486). The primary outcomes were early acute rejection (EAR) and repeated early acute rejection (RR). We defined EAR as the occurrence of a biopsy-proven AR within 3 months after transplantation.

RESULTS

The development of EAR was dependent on the number of A alleles in recipients and showed a dose-response relationship (P = 0.002). When we combined the number of A alleles in both donor and recipient, episodes of EAR and RR were more prevalent as the allelic number increased (A allelic number 0 & 1, 2 versus 3 & 4, P = 0.048; 0 & 1 versus 3 & 4, P = 0.006). Statistical significance was preserved after multivariate analysis of sex, HLA mismatch and type of donor with the recipient's age as the continuous term. Also, graft survival was different according to the presence of the A allele, i.e. recipients carrying A allele (+) grafts showed poor graft survival (P = 0.008 by a log-rank test). Again, the number of A alleles affected graft survival as the recipients who carried more A alleles had poor graft survival (A allele number 0 & 1 versus 2 versus 3 & 4, P = 0.011; 0 & 1 versus 3 & 4, P = 0.08; 0 & 1 versus 2, P = 0.002; by a log-rank test). All of the participants were wild-type homozygotes for CCR5Delta32.

CONCLUSIONS

The A allele of CCR5 59029G>A was a risk factor for EAR and RR. As the number of A alleles increased, episodes of EAR were more frequently observed.

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 prediction of renal transplant outcome

PURPOSE OF REVIEW

In the present study, we reviewed recent publications regarding potential genetic predictors of transplant outcome, including acute rejection, metabolism of immunosuppressive medications, long-term transplant outcome, and posttransplant complications.

RECENT FINDINGS

Recent studies are based on the candidate gene analysis; specifically, cytokine genes and innate immune response molecules present popular targets for studies of acute rejection and long-term outcome. Pharmacogenomic studies are mostly focused on the genes of drug targets or the corresponding enzymes metabolizing the drug. Posttransplant complications (i.e. infections, diabetes, and malignancies) are associated with a variety of genes of different pathways. Most of the studies are based on just recipient, but not donor, genotype analysis. Positive results are balanced by reports of no association when evaluating the same genetic polymorphisms. Some of the reports might be affected by insufficient study design, including small sample size, lack of adjustment for potential confounders, and multiple comparisons.

SUMMARY

The field remains controversial because of differences in populations, study design, and statistical methods. Studies are based on candidate gene analysis; however, genome-wide association studies are lacking. Future research should be directed at better designed studies, larger sample size, evaluating both recipients and donors, and implementation of genome-wide association studies.

Moving targets: cell migration inhibitors as new anti-inflammatory therapies

The pharmaceutical industry has targeted various types of molecules to subdue inflammatory diseases. Drugs that disrupt cell migration appear particularly promising in clinical trials and in many animal models of inflammatory disease. Cell migration inhibitors not only interfere with migration of cells to a tissue, but also can affect other necessary processes such as mediator release and angiogenesis. However, the question is whether drugs that target adhesion molecules or chemoattractant receptors will prove superior to drugs that target other molecular types. This review proclaims the virtues of targeting cell migration-related molecules for development of new anti-inflammatory and anti-tumor based drugs. It is likely that cell migration inhibitors will transform the way in which many human inflammatory diseases and cancers are treated.

Chemokines and transplant vasculopathy

Transplant vasculopathy (TV) remains the leading cause of late death among heart transplant recipients. Transplant vasculopathy is characterized by progressive neointimal proliferation, leading to ischemic failure of the allograft. Multiple experimental and clinical studies have shown that injury to the graft at various stages of transplantation can be a risk factor for development of transplant vasculopathy. The hallmark of cardiac allograft injury is the infiltration of leukocytes. Recruitment of leukocytes requires intercellular communication between infiltrating cells, endothelium, parenchymal cells, and components of extracellular matrix. These events are mediated via the generation of adhesion molecules, cytokines, and chemokines. The chemokines, by virtue of their specific cell receptor expression, can selectively mediate the local recruitment/activation of distinct leukocytes/cells, allowing for migration across the endothelium and beyond the vascular compartment. This report provides a comprehensive review of the chemokines that participate in the development of transplant vasculopathy.

Relevance of MICA and other non-HLA antibodies in clinical transplantation

The clinical importance of HLA-specific antibodies for organ allograft outcome is well established. In the past few years, there has been an increasing interest in non-HLA antigens as targets of injury in organ transplant recipients. This increased interest has been spurred by the fact that HLA-identical kidney transplants also undergo immunological rejections. Polymorphisms within non-HLA genes associated with evoking an immune response to alloantigens are currently being studied for their association with transplant outcome. Non-HLA antigens, such as the polymorphic MHC class I-related chain A (MICA), expressed on endothelial cells have been implicated in the pathogenesis of hyperacute, acute and chronic organ allograft rejections. Use of endothelial cells as targets may clarify the specificities of other clinically relevant non-HLA antibodies in graft rejections. This review summarizes past and current knowledge of the clinical importance and specificities of non-HLA antibodies, and mechanisms by which these antibodies may contribute to graft destruction in clinical transplantation. The aims of current research into the role of non-HLA antigens and their genetics in predicting outcome are to develop an improved insight into the basic science of transplantation and to develop a risk or prognostic index for use in the clinical setting. Non-HLA antibody responses are receiving increasing interest in acute and chronic rejection and specificity, affinity, and pathogenicity need to be investigated to estimate their contribution. Undoubtedly, this will continue to be an area of interest in terms of fully understanding the role of non-HLA antigens as targets of immune-mediated injury and the potential for clinical intervention.

Association of MCP-1 and CCR2 polymorphisms with the risk of late acute rejection after renal transplantation in Korean patients

Among the factors modulating transplant rejection, chemokines and their respective receptors deserve special attention. Increased expression of monocyte chemoattractant protein-1 (MCP-1) and its corresponding receptor (chemokine receptor-2, CCR2) has been implicated in renal transplant rejection. To determine the impact of the MCP-1-2518G and CCR2-64I genotypes on renal allograft function, 167 Korean patients who underwent transplantation over a 25-year period were evaluated. Genomic DNA was genotyped using polymerase chain reaction followed by restriction fragment length polymorphism analysis. Fifty-five (32.9%) patients were homozygous for the MCP-1-2518G polymorphism. Nine (5.4%) patients were homozygous for the CCR2-64I polymorphism. None of the investigated polymorphism showed a significant shift in long-term allograft survival. However, a significant increase was noted for the risk of late acute rejection in recipients who were homozygous for the MCP-1-2518G polymorphism (OR, 2.600; 95% CI, 1.125–6.012; P = 0.022). There was also an association between the MCP-1-2518G/G genotype and the number of late acute rejection episodes (P = 0.024). Although there was no difference in the incidence of rejection among recipients stratified by the CCR2-V64I genotype, recipients with the CCR2-V64I GG genotype in combination with the MCP-1-2518G/G genotype had a significantly higher risk of acute or late acute rejection among the receptor-ligand combinations (P = 0.006, P = 0.008, respectively). The MCP-1 variant may be a marker for risk of late acute rejection in Korean patients.

Genetic variability of major inflammatory mediators has no impact on the outcome of kidney transplantation

BACKGROUND

Functionally relevant polymorphisms in genes of the Th1 and Th2-inflammatory pathway influence the susceptibility to acute rejection (AR), chronic allograft nephropathy (CAN), and subclinical rejection (SR) as well as graft survival after renal transplantation. Because these findings have not been validated, we sought confirmatory evidence of these associations in a larger group of renal transplant recipients.

METHODS

A total of 436 kidney transplant recipients were genotyped for 9 single nucleotide polymorphisms (TNF-alpha-308G/A, MCP-1-2518A/G, RANTES-403G/A, -109T/C and -28C/G, CCR2+190G/A, IFN-gamma+874A/T, TGF-beta+869T/C and +915G/C) and for the 32-bp indel polymorphism in CCR5. The effects of these polymorphisms on the incidence of AR, SR, CAN and graft survival were analyzed in single locus and haplotype models.

RESULTS

Single locus analysis revealed that there was no significant difference in the distribution of the genotype frequencies between patients with and without AR, and between patients with CAN or SR, and individuals without CAN. Furthermore, no influence of any of the polymorphisms on the long-term graft survival was observed. Haplotype [TGF-beta +869G; TGF-beta +915C] seemed to be associated with the presence of SR (odds ratio: 3.45, 95% confidence interval: 1.19 - 9.99, P=0.023), but the association was nonsignificant due to the insufficient power.

CONCLUSION

In contrast to previous allelic association studies, neither of the polymorphisms has been associated with the outcome of kidney transplantation in the single locus analysis nor in the haplotype model. Our findings reinforce the need for more rigorous research compliant with the currently accepted standards for polymorphism-disease association studies.

Analysis of CCR5, CCR2, SDF1 and RANTES gene polymorphisms in subjects with HIV-related PML and not determined leukoencephalopathy

Progressive Multifocal Leukoencephalopathy (PML) is a fatal demyelinating disease of the central nervous system (CNS) caused by JC virus (JCV), a human polyomavirus that can lytically infect and destroy the oligodendrocites in immunosuppressed individuals. After the introduction of highly active antiretroviral therapy (HAART) for AIDS treatment, a PML-like leukoencephalopathy, known as non-determined leukoencephalopathy (NDLE), has also been observed. Since a number of host genetic factors have been identified as having an impact on susceptibility to HIV-1 infection and in the progression to AIDS and death, in this work we analysed the pattern of distribution of different chemokine and chemokine receptor polymorphisms that seem to be involved in HIV+ neurological diseases. The CCR5, RANTES, CCR2 and SDF1 genes were molecularly analysed in 84 HIV+ HAART treated subjects: 55 without neurological disorders (HIV+), 12 HIV+ NDLE and 17 HIV+ PML patients. The RANTES -403 G/A polymorphism was significantly associated with NDLE. These data suggest that mutation of the RANTES allele can predispose to the induction of demyelination similarly to what has been observed in Multiple Sclerosis (MS) and may suggest a possible explanation for the development of leukoencephalopathy without detection of JCV.

Role of beta3 integrin in acute renal allograft rejection in humans

BACKGROUND AND OBJECTIVES

Beta3 Integrin may play a role in the process of acute rejection by increasing leukocyte adhesion to the endothelium, cytotoxic T lymphocyte activation, and platelet aggregation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

For investigation of the role of beta3 integrin in the pathogenesis of acute rejection, this study examined the surface expression of beta3 integrin on leukocyte subsets and analyzed a common single-nucleotide polymorphism in exon 2 of the gene encoding the beta3 subunit that generates two beta3 integrin isoforms, termed Pl(A1) and Pl(A2). Pl(A) genotype was determined in blood samples from 445 renal allograft recipients at two centers. Patients were then grouped by Pl(A) genotype, and clinical outcomes as recorded in a preexisting database were analyzed.

RESULTS

Although almost all monocytes express beta3 integrin, its expression was also found on all leukocyte subsets, including T, B, and NK cells. The percentage of patients who experienced acute rejection was noted to be significantly higher in those with Pl(A1)/Pl(A1) (TT) genotype versus patients with the Pl(A1)/Pl(A2) or Pl(A2)/Pl(A2) (CT or CC) genotypes (33% for TT versus 20% for CT or CC). In a multivariate analysis, the Pl(A1)/Pl(A1) (TT) genotype remained significantly associated with acute rejection. Patients with Pl(A1)/Pl(A1) (TT) genotype also exhibited a higher number of acute rejection episodes per patient.

CONCLUSIONS

The Pl(A1)/Pl(A1) (TT) genotype is associated with an increased incidence of acute renal allograft rejection in humans, supporting a role for beta3 integrin in the pathophysiology of acute rejection.

Antibodies against MICA antigens and kidney-transplant rejection

BACKGROUND

Good HLA-A, HLA-B, and HLA-DR matches do not guarantee rejection-free renal transplantation. Some kidney transplants fail despite such matches, suggesting that other antigens might be targets for rejection. Major-histocompatibility-complex (MHC) class I-related chain A (MICA) antigens are polymorphic and can elicit antibody production. We sought to determine whether an immune response to MICA antigens might play a role in the failure of kidney allografts.

METHODS

Pretransplantation serum samples from 1910 recipients of kidney transplants from deceased donors were tested for anti-MICA antibodies with an assay in which single MICA antigens were attached to polystyrene microspheres.

RESULTS

Antibodies against MICA alleles were detected in 217 of the 1910 patients (11.4%). The presence of MICA antibodies was associated with renal-allograft rejection. The mean (+/-SE) 1-year graft-survival rate was 88.3+/-2.2% among recipients with anti-MICA antibodies as compared with 93.0+/-0.6% among recipients without anti-MICA antibodies (P=0.01). Among recipients of first kidney transplants, the survival rate was even lower among MICA antibody-positive patients (87.8+/-2.4%) than among MICA antibody-negative recipients (93.5+/-0.6%, P=0.005). In addition, the association of MICA sensitization with reduced graft survival was more evident in kidney-transplant recipients with good HLA matching: among 326 recipients who received well-matched kidneys (0 or 1 HLA-A plus HLA-B plus HLA-DR mismatch), sensitization against MICA was associated with poorer allograft survival (83.2+/-5.8% among those with anti-MICA antibodies vs. 95.1+/-1.3% among those without such antibodies, P=0.002).

CONCLUSIONS

Presensitization of kidney-transplant recipients against MICA antigens is associated with an increased frequency of graft loss and might contribute to allograft loss among recipients who are well matched for HLA.

Polymorphisms in chemokine receptor genes and susceptibility to Kawasaki disease

Kawasaki disease (KD) is an acute vasculitis occurring in young children. Its aetiology is unknown, but an infectious agent is assumed. Increased levels of proinflammatory cytokines and chemokines have been reported in KD. Genetic variation in these genes and the receptors for these genes could influence the regulation of cytokines and chemokines. In a case-control study of 170 Dutch Caucasian KD patients and 300 healthy Dutch Caucasian controls, common genetic variants in chemokine receptor genes CCR3, CCR2, CCR5, CX3CR1, CXCR1 and CXCR2 were analysed. Of the eight studied single nucleotide polymorphisms (SNPs) in the CCR3-CCR2-CCR5 gene cluster, four showed a significant association with susceptibility to KD. Moreover the CCR5-Delta32 was observed with an allele frequency of 10.7% in the control population compared to 6.5% in the KD patients (P = 0.04). Two haplotypes of the CCR3-CCR2-CCR5 gene-cluster appear to be at risk haplotypes for KD and one a protective haplotype. No association was observed with the studied SNPs in CX3CR1, CXCR1 and CXCR2. In conclusion, in a Dutch cohort of KD patients an association of KD occurrence with common genetic variants in the chemokine receptor gene-cluster CCR3-CCR2-CCR5 was observed.

Chemokines and chemokine receptors in renal transplantation — from bench to bedside

Attraction of mononuclear cells to sites of inflammation requires a close interplay of the inflammatory signal presented via chemokines and specific receptors on effector cells. First studies on acute renal transplant rejection demonstrated the involvement of CC-chemokines, such as RANTES, MIP-1alpha, MIP-1beta and MCP-1, as well as CXC-chemokines such as IL-8 and IP-10, correlating with expression of the corresponding chemokine receptors, CCR1, CCR5 and CCR2 as well as CXCR3. Since then, the pathophysiologic relevance has been extended to chronic allograft nephropathy and transplant glomerulopathy. Chemokine expression can be triggered by different stimuli, e.g. brain death, ischemia, HLA-mismatch and infection. Furthermore, anti-inflammatory chemokines have been identified. Chemokine receptor 7, e.g. enhances homing of lymphocytes to lymphatic tissues and the Duffy antigen receptor, DARC, a non-specific receptor that binds and inactivates different chemokines. While measurement of chemokine expression in clinical transplantation may facilitate the differential diagnosis of allograft dysfunction, knowledge of the chemokine network has also widened the understanding of transplant rejection and opened novel therapeutic approaches. Observations from humans with mutations of the chemokine network as well as transplantation of animals with targeted deletions in this system suggest that manipulations of chemokine signalling may improve the success rates of transplantation. Blocking chemokines unselectively with Met-RANTES or specifically with small molecule inhibitors of various chemokine receptors has lead to improved outcome in animal models. Currently, first human trials are under way to investigate drugs that stimulate lymphocyte homing. Inhibitors of CCR1 and CCR5 are being tested for other human diseases and may eventually be available in transplantation. Nonetheless, chemokine blockade my rather serve as an adjunct in the management of transplant recipients than a new "magic bullet".

Analysis of CC chemokine receptor 5 and 2 polymorphisms and renal transplant survival

Chronic rejection is an immune process leading to graft failure. By regulating the trafficking of leukocytes, chemokines and chemokine receptors are thought to be one of the reasons causing acute renal rejection (ARE), which increases the possibility of chronic rejection and organ destruction. This study was designed to investigate, in the Turkish population, an association of chemokine receptor genetic variants, CCR2V641, CCR5-59029-A/G, CCR5-Delta32 and acute renal rejection after renal transplant surgery. We carried out our study in 85 Turkish renal transplant patients (45 men, 40 women; mean age 39 +/- 2 years) by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) techniques. We found no significant difference in the incidence of rejection among patients possessing or lacking CCR5-Delta32. For the groups with and without acute renal rejection, we found a significant difference between the groups in A and G allele distribution in both CCR2V641and CCR559029 gene variants (p = 0.003 and p = 0.003, respectively). According to our findings, the risk of acute rejection in renal transplantation may be associated with genetic variation in the chemokine receptor genes CCR5-59029 and CCR2V641 in Turkey, and studies on these gene polymorphisms could be an ideal target for future interventions intended to prevent renal transplant loss.

Prevalence of CCR5Delta32 polymorphism in long-term survivors of heart transplantation

BACKGROUND

CC chemokine receptor 5 (CCR5) contributes to the alloimmune response following solid organ transplantation. In individuals homozygous for the CCR5Delta32 mutation, the receptor is inactive and lymphocyte recruitment and leukocyte trafficking during rejection are inhibited. A significant improvement in graft survival following renal transplantation has been observed in homozygous CCR5Delta32 patients, although conflicting data exist. To determine whether CCR5Delta32 homozygous heart transplant recipients may also benefit compared to those with a normally functioning CCR receptor, the proportion of patients with CCR5Delta32 mutation was examined in a large cohort of patients surviving for a long period after heart transplantation.

METHODS

The prevalence of CCR5 genotype was identified in patients who had survived >or=7 years after heart transplantation. Genotyping was performed centrally by polymerase chain reaction (PCR).

RESULTS

A total of 555 patients were recruited at three heart transplant centers in Germany. Of these, 442 patients (79.6%) were homozygous for the wild-type allele, 106 (19.1%) were heterozygous for CCR5Delta32 and 7 (1.3%) were homozygous for CCR5Delta32. No statistically significantly differences were observed between the incidence of CCR5Delta32 homozygosity in the study population and the estimated incidence in the normal population.

CONCLUSIONS

In the absence of a control arm, it cannot be established if homozygous carriers of the CCR5Delta32 allele experience a long-term survival benefit following heart transplantation that may be masked by underrepresentation of the CCR5Delta32 allele in recipients of a heart transplant. To answer this question, the prevalence of CCR5Delta32 homozygosity needs to be established in patients awaiting heart transplantation.

Polymorphisms in CCL2&CCL5 chemokines/chemokine receptors genes and their association with diseases

BACKGROUND

Chemokines and chemokine receptors are major mediators of leukocyte trafficking into the sites of the immune response. They participate in defence against microbial infection, in Th1/Th2 polarization of the immune response, allograft rejection and angiogenesis/angiostasis as well as in tumorigenesis and metastasis. To date, several functional polymorphisms of chemokine and chemokine receptor genes have been discovered that are able to deregulate chemokine system and, therefore, they may interfere with the pathogenesis of a large number of inflammatory and other diseases. In this review we focus on the known polymorphisms of two chemokines: CCL2, CCL5 and their corresponding receptors (CCR2, CCR5) and we also discuss their associations with susceptibility and progression to selected immune-mediated diseases.

METHODS AND RESULTS

Based on relevant literature this article gives a short overview of case-control and family studies regarding effect of the genetic factors on diseases such as coronary artery disease, systemic lupus erythematosus, diabetes mellitus, lung diseases and others.

CONCLUSION

Recent advance in the identification of chemokine genetic background of the diseases could provide opportunity for pharmacological treatment. However, we need more information about posttranscriptional events to understand functional relevance of polymorphisms and to discovery new avenues to blocking disease development.

Human genetic polymorphisms affecting HIV-1 diseases

Human immunodeficiency virus type 1 (HIV-1) infection is generally characterized by a long-term, chronic disease course that gradually progresses to acquired immunodeficiency syndrome (AIDS). However, a small fraction of HIV-1-infected individuals remain both clinically and immunologically healthy for 10 years or more after seroconversion. Conversely, the disease of another significant fraction is characterized by an extremely rapid progression to AIDS within 1 year. There are also individuals not infected with HIV-1 who have had repetitive sexual exposure to HIV-1 in extremely high-risk situations. Determining the host factors involved in these different susceptibility and disease courses would be helpful for better understanding AIDS and its control. Today, a worldwide scientific endeavor called the Human Genome Project has completed the production of a full-length sequence of the 3 billion base pairs that make up the human genome. The Human Genome Project has also revealed the presence of variation in human genomes. Relating these genetic differences to human phenotypes offers a very attractive prospect for a genetic understanding of the different sensitivities to various human diseases, including cancer, brain and heart diseases, allergy, and infectious diseases. In this review, we present examples of human genetic variation that can affect HIV-1 infection and disease progression.

Relationship of five inflammatory gene polymorphisms with morbidity and mortality in 533 patients admitted to an ICU

BACKGROUND

The aim of this study was to analyze the association of polymorphisms of five candidate genes with the outcome of consecutive patients admitted to a medical ICU.

MATERIALS AND METHODS

The study population was prospectively recruited. Inclusion criteria were admission to the ICU and written informed consent by the patients or their relatives. A total of 533 patients were recruited. The morbidity was assessed by SAPS II Score. Outcome data of in hospital mortality and length of ICU and hospital stay were obtained. Genotyping for genetic polymorphisms (CRP 1059, IL1B -511, CTGF -477, CCR2 64VI, IL6 -174) were performed by allele-specific fluorogenic oligonucleotide probes (TaqMan analysis).

RESULTS

All of the investigated polymorphisms were not associated with an altered outcome. There was no difference in morbidity and ICU or in-hospital mortality (neither in cross tabs analysis nor in Kaplan Meier or Cox regression analysis including age, gender and diagnosis as covariates) between the different genotypes.

CONCLUSIONS

Genotyping of the investigated polymorphism for risk stratification of patients admitted to ICU does not seem to be appropriated.

Chemotactic cytokine receptor 5 (CCR5) gene promoter polymorphism (59029A/G) is associated with diabetic nephropathy in Japanese patients with type 2 diabetes: a 10-year longitudinal study

We previously showed that polymorphisms of the promoter area of chemokine receptor 5 (CCR5) gene (59029G/A) and its agonist, regulated upon activation, normal T-cell expressed and secreted (RANTES) gene (-28C/G) were new candidates for susceptibility to diabetic nephropathy. The aim of this study was to confirm the effect of these polymorphisms on the development and progression of diabetic nephropathy. We performed a 10-year retrospective study of 191 Japanese type 2 diabetic patients with normoalbuminuria at baseline. The subjects were classified into two groups: (1) those with persistent normoalbuminuria (group N) and (2) those with progression from normoalbuminuria to microalbuminuria or overt proteinuria (group P). Then, their association with CCR5 59029G/A and RANTES -28C/G polymorphisms was assessed. The frequency of the RANTES -28G(+) genotype did nor differ between the two groups, but the CCR5 59029A(+) genotype had a significantly higher frequency in group P than in group N (83% versus 71%, p=0.04). By discriminant analysis, only the CCR5 59029A(+) genotype showed an independent positive correlation with the onset or progression of nephropathy (p=0.03, odds ratio=2.41, 95% CI=1.09-5.33). Therefore, the CCR5 59029A(+) genotype seems to be related the etiology of diabetic nephropathy in Japanese type 2 diabetics.

CCR5 deficiency increases risk of symptomatic West Nile virus infection

West Nile virus (WNV) is a reemerging pathogen that causes fatal encephalitis in several species, including mouse and human. Recently, we showed that the chemokine receptor CCR5 is critical for survival of mice infected with WNV, acting at the level of leukocyte trafficking to the brain. To test whether this receptor is also protective in man, we determined the frequency of CCR5Δ32, a defective CCR5 allele found predominantly in Caucasians, in two independent cohorts of patients, one from Arizona and the other from Colorado, who had laboratory-confirmed, symptomatic WNV infection. The distribution of CCR5Δ32 in a control population of healthy United States Caucasian random blood donors was in Hardy-Weinberg equilibrium and CCR5Δ32 homozygotes represented 1.0% of the total group (n = 1,318). In contrast, CCR5Δ32 homozygotes represented 4.2% of Caucasians in the Arizona cohort (odds ratios [OR] = 4.4 [95% confidence interval [CI], 1.6–11.8], P = 0.0013) and 8.3% of Caucasians in the Colorado cohort (OR = 9.1 [95% CI, 3.4–24.8], P < 0.0001). CCR5Δ32 homozygosity was significantly associated with fatal outcome in the Arizona cohort (OR = 13.2 [95% CI, 1.9–89.9], P = 0.03). We conclude that CCR5 mediates resistance to symptomatic WNV infection. Because CCR5 is also the major HIV coreceptor, these findings have important implications for the safety of CCR5-blocking agents under development for HIV/AIDS.

CCR5, RANTES and CX3CR1 polymorphisms: possible genetic links with acute heart rejection

BACKGROUND

The inflammation response is modulated by the elaborated chemokine-chemokine receptor system, which also plays an important role in the development of acute rejection (AR). In this study, we hypothesized that functional genetic variants of some of these modulatory proteins might influence the outcome of AR.

METHODS

In a retrospective analysis of a cohort of heart transplanted patients (n=158), we examined eight polymorphisms in four genes implicated in this inflammatory process: RANTES, CCR5, CCR2 and CX3CR1. On the basis of timing occurrence, AR episodes (grade>or= 3A) were classified in "early" (0-3 months posttransplantation; EAR) or "late" outcomes (4-12 months posttransplantation; LAR).

RESULTS

The incidences of EAR and LAR were 57.6% and 41%, respectively. Number of LAR episodes was significantly higher in subjects that have already experienced one or more EAR episodes, as compared to subjects that had no EAR (median [25%-75%]: 4 () vs. 1 [1-2.5] respectively; P<0.0001). Statistical univariate analysis showed that none of the mentioned polymorphisms were correlated with EAR or LAR. However, allele-allele association analysis showed that subjects carrying both the CX3CR1 249I allele and CCR5 No-E haplotypes were significantly at lower risk of experiencing EAR (OR=0.2 [95%-CI=0.1-0.5], P=0.001). In contrast subjects carrying both the CCR5 E haplotype and the RANTES -403A allele were significantly at higher risk to develop LAR (OR=8.1 [95%-CI=2.3-28.7], P=0.002).

CONCLUSIONS

This exploratory study in heart transplantation suggests that the outcomes of EAR and LAR episodes may be influenced by genetic variant interactions such as "CX3CR1 249I*CCR5 No-E" and "CCR5 E*RANTES -403A."

Risk of diabetic nephropathy in type 1 diabetes is associated with functional polymorphisms in RANTES receptor gene (CCR5): a sex-specific effect

Chemokines and their receptors have been implicated in the development of diabetic nephropathy. To determine whether the risk of diabetic nephropathy is influenced by two functional polymorphisms in the regulated upon activation normal T-cell expressed and secreted (RANTES) receptor gene (CCR5), we recruited patients with type 1 diabetes, including 496 case subjects with overt proteinuria or end-stage renal disease and 298 control subjects with normoalbuminuria. Male carriers of the 59029G allele, which is associated with diminished expression of CCR5 on the surface of immunocompetent cells, had significantly higher risk of developing diabetic nephropathy than noncarriers (OR [95% CI] 1.9 [1.2-3.0]). Similarly, male carriers of the 32-bp deletion, which causes truncation of the protein, had significantly higher risk of diabetic nephropathy than noncarriers (2.3 [1.3-4.2]). Combining both polymorphisms, three haplotypes were distinguished: one nonrisk haplotype carrying the 59029A allele and the 32-bp insertion and two risk haplotypes carrying the 59029A allele with the 32-bp deletion and carrying the 59029G allele with the 32-bp insertion. The distribution of these haplotypes differed significantly (P < 0.00001) in men with and without diabetic nephropathy but was not associated with diabetic nephropathy in women. In conclusion, two functional polymorphisms in CCR5 that decrease expression of the RANTES receptor on immunocompetent cells are associated with increased risk of diabetic nephropathy in type 1 diabetes, but only in men.

Donor genomics influence graft events: the effect of donor polymorphisms on acute rejection and chronic allograft nephropathy

BACKGROUND

Organs procured from deceased donors emanate from individuals with diverse genetic backgrounds. Donor organs, therefore, may vary in their response to injury and immune stimuli in a genetically determined manner. We assessed polymorphisms from 244 renal allograft donors to better understand the impact of donor polymorphisms on selected transplant outcomes.

METHODS

Donor genomic DNA restriction fragment length polymorphisms were assayed for evidence of common cytokine [interleukin (IL)-2, IL-6, IL-10, tumor necrosis factor (TNF)-alpha, TGF-beta, interferon (IFN)-gamma] and chemokine (CCR2, CCR5) polymorphisms. Associations between donor polymorphisms and graft events were determined using chi-square, linear regression, and Kaplan-Meier analyses.

RESULTS

Several genotypic polymorphisms demonstrated a modest association with acute rejection, including the transforming growth factor (TGF)-beta T/C codon 10 (P= 0.027) and the CCR5 G/A 59029 (P= 0.039) genes by chi-square analysis. Notably, the presence of the T allele in the IFN-gamma gene (+874) demonstrated a highly significant association with biopsy-proven chronic allograft nephropathy (P < 0.008). This association remained highly significant in a multiple linear regression model that incorporated biopsy-proven acute rejection as a covariate.

CONCLUSION

These data suggest that many of the donor polymorphisms studied in this analysis may influence a recipient's immune response to a renal allograft. However, their greatest impact may be demonstrated in long-term outcomes.

Is the CCR5-59029-G/G genotype a protective factor for cardiomyopathy in Chagas disease?

Investigated were two CCR5 gene polymorphisms, the CCR5 Delta 32 deletion and the pCCR5 59029 A-->G promoter point mutation, in 107 ethnically mixed Venezuelan patients serologically positive for Trypanosoma cruzi (34 asymptomatic, 38 arrhythmic, 35 cardiomyopathic). No difference in the distribution of CCR5 Delta 32 among asymptomatic and symptomatic patients was found. We have observed an increase of the 59029-G phenotype among asymptomatic compared with symptomatic chagasic patients (68% vs. 58%), in agreement with previously reported data (57% vs. 31%). This frequency difference, although not statistically significant, is more marked when the 59029-G allele is present in homozygous form. However, a similar distribution of the G/G genotype is present among asymptomatic patients and patients with heart failure. Because it has been reported that the 59029G/G genotype associates with lower CCR5 expression, 37% of our T. cruzi-infected patients with heart failure are genetically predisposed to express low levels of CCR5 on the surface of CD8(+) T cells, contrary to what would be expected if an inflammatory response is required for severe cardiac damage. If confirmed, the possible protection that might be conferred by the G/G genotype may be due to the existence of other genes in linkage disequilibria.

?-chemokine receptor expression in idiopathic inflammatory myopathies

Beta-chemokines attract and activate T cells and monocytes and have a key role in chronic inflammation. Certain beta-chemokines, such as monocyte chemoattractant protein-1 (MCP-1), have been reported to be upregulated in the idiopathic inflammatory myopathies (IIM). We studied the distribution of beta-chemokine receptors in polymyositis (PM), sporadic inclusion-body myositis (sIBM), dermatomyositis (DM), and control samples. CCR1-5 were localized to blood vessels in all samples. In addition, increased endothelial expression of CCR2A was observed in IIM. Subsets of inflammatory cells, identified as macrophages and T cells, in all three types of IIM expressed CCR2A, CCR2B, CCR3, CCR4, and CCR5. In contrast to an earlier report, we found CCR2B to be the most prominent MCP-1 receptor on inflammatory cells in IIM, especially in PM and sIBM. Strong CCR4 expression was present on myonuclei of regenerating muscle fibers. The prominence of the CCR2 receptors further underlines the importance of the interaction with their ligand MCP-1 in the immunopathogenesis of IIM and puts CCR2B forward as a potential target for future therapeutic intervention.

Fractalkine and inflammatory diseases

The migration of leukocytes into inflamed peripheral tissues and lymphoid organs involves a cascade of molecular events finely regulated by cell adhesion molecules and chemokines. Fractalkine/CX3CL1 is a membrane-bound chemokine that functions not only as a chemoattractant but also as an adhesion molecule, and is expressed on endothelial cells activated by proinflammatory cytokines. The fractalkine receptor, CX3CR1, is expressed on cytotoxic effector lymphocytes including NK cells and cytotoxic effector T cells (T(CE)), mature monocytes/macrophages, and mucosal dendritic cells, all of which play important roles in elimination of pathogens and cancer cells. Recently, accumulating evidence in both clinical studies and animal disease models has shown that fractalkine is also involved in the pathogenesis of various chronic inflammatory diseases, such as rheumatoid arthritis and atherosclerosis. This article reviews the unique functions of fractalkine and its pathophysiological roles in various clinical conditions.

The role of nitric oxide in renal transplantation

This review discusses the concept that nitric oxide synthase (NOS) may orchestrate both the inflammatory response to the renal allograft and anti-inflammatory defense in the graft itself. NO is produced by endothelial, epithelial, as well as inflammatory cells. In the setting of transplantation, the endothelium is the first lining to be subjected to the early response to injury. In turn, activated endothelial cells facilitate leukocyte recruitment, immune-mediated injury, and angiogenesis. On activation by inflammatory stimuli, endothelial cells up-regulate multiple vasoactive substances, oxygen radicals, cytokines, chemokines, and growth factors. Therefore, endothelial integrity, especially the expression of protecting vasoactive agents, such as NO, may be a key factor in resistance or sensitivity to transplantation-mediated injury. Thus, evaluating the mechanisms by which NO is involved in either protecting or injuring the transplanted allogeneic kidney is important for our understanding of renal allograft rejection. This review focuses on the role of NO in the inflammatory endothelial-leukocyte interactions, which are implicated in acute and chronic rejection of the transplanted kidney.

Chemokines in the Pathogenesis of Vascular Disease

Our increasing appreciation of the importance of inflammation in vascular disease has focused attention on the molecules that direct the migration of leukocytes from the blood stream to the vessel wall. In this review, we summarize roles of the chemokines, a family of small secreted proteins that selectively recruit monocytes, neutrophils, and lymphocytes to sites of vascular injury, inflammation, and developing atherosclerosis. Chemokines induce chemotaxis through the activation of G-protein-coupled receptors, and the receptors that a given leukocyte expresses determines the chemokines to which it will respond. Monocyte chemoattractant protein 1 (MCP-1), acting through its receptor CCR2, appears to play an early and important role in the recruitment of monocytes to atherosclerotic lesions and in the formation of intimal hyperplasia after arterial injury. Acute thrombosis is an often fatal complication of atherosclerotic plaque rupture, and recent evidence suggests that MCP-1 contributes to thrombin generation and thrombus formation by generating tissue factor. Because of their critical roles in monocyte recruitment in vascular and nonvascular diseases, MCP-1 and CCR2 have become important therapeutic targets, and efforts are underway to develop potent and specific antagonists of these and related chemokines.

The chemokine receptor CCR5-Delta32 gene mutation is not protective against Alzheimer's disease

Chronic local inflammatory reaction involving reactive microglia is one of the major pathological events in Alzheimer's disease (AD). There is growing evidence that the chemokine receptor CCR5 is up-regulated in AD brain and plays a role in the recruitment and accumulation of microglia in senile plaques. A 32-base pair deletion in the CCR5 gene (CCR5-Delta32 mutant allele) confers resistance to HIV-1 infection by preventing expression of the receptor on the cell surface. Several other reports have shown a similar protective effect of CCR5-Delta32 mutation towards certain chronic inflammatory diseases. Given the potential importance of CCR5 in brain inflammation, we hypothesized that individuals carrying the CCR5-Delta32 allele would show a reduced risk of AD. So, we performed a case-control study in 376 Spanish AD patients and 369 healthy controls. The frequency of the CCR5-Delta32 allele in our AD sample was 7.8%, not significantly different from our control sample group (5.8%). The present study indicates that the CCR5-Delta32 allele is not a preventive factor for AD.

Identifying Chemokines as Therapeutic Targets in Renal Disease: Lessons from Antagonist Studies and Knockout Mice

Chemokines, in concert with cytokines and adhesion molecules, play multiple roles in local and systemic immune responses. In the kidney, the temporal and spatial expression of chemokines correlates with local renal damage and accumulation of chemokine receptor-bearing leukocytes. Chemokines play important roles in leukocyte trafficking and blocking chemokines can effectively reduce renal leukocyte recruitment and subsequent renal damage. However, recent data indicate that blocking chemokine or chemokine receptor activity in renal disease may also exacerbate renal inflammation under certain conditions. An increasing amount of data indicates additional roles of chemokines in the regulation of innate and adaptive immune responses, which may adversively affect the outcome of interventional studies. This review summarizes available in vivo studies on the blockade of chemokines and chemokine receptors in kidney diseases, with a special focus on the therapeutic potential of anti-chemokine strategies, including potential side effects, in renal disease.

Duffy antigen receptor and genetic susceptibility of African Americans to acute rejection and delayed function

BACKGROUND

The unique distribution of the alleles for the Duffy antigen receptor complex (DARC) that binds to chemokines may be associated with the rates of acute rejection and delayed allograft function (DGF) among African Americans.

METHODS

A prospective, multicenter cohort study enrolled 222 African American recipients of cadaveric renal allografts from eight adult transplant centers. Subjects were typed by allele-specific polymerase chain reaction (ASPCR) for the polymorphism at position 535 that determines the level of transcription. Associations of DARC genotypes were examined in Cox hazards models with episodes of acute rejection and in logistic regression models with the development of DGF.

RESULTS

FyB Null homozygosity was observed among 67% of the recipients. Fifteen percent of the study cohort experienced at least one episode of acute rejection, and the incidence of DGF was 42.5%. The number of FyB Null alleles and FyB Null homozygosity had no detectable association with the rate of acute rejection (P > 0.50) or with the development of DGF (P > 0.50).

CONCLUSION

The susceptibility of African American recipients to acute rejection and to DGF was not confirmed to be associated with DARC alleles or genotype. Future studies should exclude a potential role of donor-related DARC in transplant outcomes.

Candidate gene polymorphisms in solid cancers

Accumulation of information from scientific advances in genetics and biotechnology has accelerated research investigating the inherent individual variation in disease susceptibility and severity. Gene polymorphisms, in particular single nucleotide polymorphisms, are being evaluated for their role in multi-factorial diseases such as cancer and inflammation. Most surgical diseases are multi-factorial and a better understanding and utilization of the information gained from such studies by clinicians/surgeons is likely to favorably influence patient outcome. In this article, we illustrate the types of genetic variation and the complexities involved in their study and discuss their potential in predicting both the occurrence and outcomes of solid cancers.

Differential role of CCR2 in islet and heart allograft rejection: tissue specificity of chemokine/chemokine receptor function in vivo

Chemokines have a pivotal role in the mobilization and activation of specific leukocyte subsets in acute allograft rejection. However, the role of specific chemokines and chemokine receptors in islet allograft rejection has not been fully elucidated. We now show that islet allograft rejection is associated with a steady increase in intragraft expression of the chemokines CCL8 (monocyte chemoattractant protein-2), CCL9 (monocyte chemoattractant protein-5), CCL5 (RANTES), CXCL-10 (IFN-gamma-inducible protein-10), and CXCL9 (monokine induced by IFN-gamma) and their corresponding chemokine receptors CCR2, CCR5, CCR1, and CXCR3. Because CCR2 was found to be highly induced, we tested the specific role of CCR2 in islet allograft rejection by transplanting fully MHC mismatched islets from BALB/c mice into C57BL/6 wild-type (WT) and CCR2-deficient mice (CCR2-/-). A significant prolongation of islet allograft survival was noted in CCR2-/- recipients, with median survival time of 24 and 12 days for CCR2-/- and WT recipients, respectively (p < 0.0001). This was associated with reduction in the generation of CD8+, but not CD4+ effector alloreactive T cells (CD62L(low)CD44(high)) in CCR2-/- compared with WT recipients. In addition, CCR2-/- recipients had a reduced Th1 and increased Th2 alloresponse in the periphery (by ELISPOT analysis) as well as in the grafts (by RT-PCR). However, these changes were only transient in CCR2-/- recipients that ultimately rejected their grafts. Furthermore, in contrast to the islet transplants, CCR2 deficiency offered only marginal prolongation of heart allograft survival. This study demonstrates the important role for CCR2 in early islet allograft rejection and highlights the tissue specificity of the chemokine/chemokine receptor system in vivo in regulating allograft rejection.

A CCR2-V64I polymorphism affects stability of CCR2A isoform

OBJECTIVE

A valine to isoleucine substitution at position 64 of CCR2 (CCR2-64I) is associated with a delay in progression to AIDS in HIV-1-infected individuals. The aim of the present study is to elucidate the molecular mechanism underlying the effect of this allele.

DESIGN

We analysed the effect of the 64I substitution on levels of expression of CCR2A and CCR2B, two CCR2 isoforms produced by alternative splicing.

METHODS

Sendai virus vector was used to express CCR2 molecules.

RESULTS

While CCR2B trafficked well to the cell surface, CCR2A, which differs from CCR2B only by the sequence of its C-terminal cytoplasmic tail, was detected predominantly in the cytoplasm. The level of expression of CCR2A-64I was significantly higher than that of CCR2A without the substitution. On the other hand, the 64I substitution did not affect levels of CCR2B expression. Pulse-chase experiments revealed that the 64I substitution increased the half-life of CCR2A in cells. When co-expressed with CCR5, CCR2A-64I interfered more severely with cell surface expression of CCR5 than did wild-type CCR2A. Furthermore, immunoprecipitation experiments showed that CCR2A co-precipitated with an immature form of CCR5.

CONCLUSION

These results suggest that CCR2A binds to CCR5 in the cytoplasm and down-modulates its surface expression. We propose that the increased ability of CCR2A-64I to down-modulate CCR5 expression might be a possible cause of a delay in HIV-1 disease progression in patients with this allele.

CC chemokine receptor 5delta32 polymorphism-a risk factor for ischemic-type biliary lesions following orthotopic liver transplantation

Ischemic-type biliary lesions are a major complication following orthotopic liver transplantation. They occur in up to 26% of liver transplant recipients. Among other factors, unknown immunologic factors have always been assumed to be partly responsible for these lesions. CC-chemokines and their receptors play a key role in postoperative immunomodulation after liver transplantation. The non-function CC-chemokine receptor 5delta32 polymorphism (CCR5delta32) has been shown to lead to a lower rate of acute rejection after kidney transplantation; in liver transplantation the role of CCR5delta32 is unclear. We investigated the influence of the CCR5delta32 after liver transplantation with special regard to ischemic-type biliary lesions. The CC-chemokine receptor-5 (CCR5) of 146 recipients was analyzed by polymerase chain reaction to detect CCR5delta32 in blood samples of patients after liver transplantation. One hundred twenty patients with wild-type CCR5 and 26 patients with CCR5delta32 (1 homozygote, 25 heterozygote) were identified. Ischemic-type biliary lesions occurred in 14 of 120 patients with wild-type CCR5 and in 8 of 26 patients with CCR5delta32 polymorphism (P = = 0.01). 5 year patient survival with CCR5delta32 and CCR5 was 70% and 85%, respectively (P =.0067). Our results show that the CCR5delta32 is a significant risk factor for the development of ischemic-type biliary lesions after liver transplantation and leads to a reduction in 5-year survival. In conclusion, the CCR5 status should be screened prospectively before liver transplantation.

Genetic determinants of arterial calcification associated with atherosclerosis

Increasing research interest has focused on arterial calcification in the setting of atherosclerosis. Many features of atherosclerosis-related calcification provide useful clinical information. For example, calcium mineral deposits frequently form in atherosclerotic plaque, and intimal arterial calcification can be used as a surrogate marker for atherosclerosis; also, calcium deposits are readily and noninvasively quantified, which is useful because greater amounts of coronary calcification predict a higher risk of myocardial infarction and death. Several mechanisms leading to calcification associated with atherosclerosis have been proposed; however, no direct testing of proposed mechanisms has yet been reported. Studies in genetically altered animals and in humans have shed light on potential genetic determinants, which in turn could form the basis for a more comprehensive understanding of the factors affecting calcification within plaque and the associated pathobiologic implications. We review proposed molecular and cellular mechanisms of atherosclerosis-associated arterial calcification, summarize genetic influences, and suggest areas in which further investigation is needed. Understanding the molecular and genetic determinants of specific structural plaque components such as calcification can provide a solid foundation for the development of novel therapeutic approaches to favorably alter plaque structure and minimize vulnerability to arterial rupture.

Chemokine receptor-dependent alloresponses

Immunologists have typically viewed alloreactivity schematically as a function of antigen presentation, expansion of alloreactive T and B cells within regional lymphoid tissues, and cellular infiltration and destruction of an allograft. Actual details of the steps between immune activation and accumulation of effector cells within a graft typically have not received much attention. However, just how cells "know" to move to and migrate within a graft or not is proving to be of increasing interest, as the chemokine-dependent mechanisms underlying leukocyte recruitment to a transplant are dissected. Experimentally, chemokine receptor targeting can prolong or induce permanent allograft survival, despite preservation of alloresponses within secondary lymphoid tissues, whereas current immunosuppressive protocols have only modest effects on chemokine production and leukocyte homing. Recent knowledge of the chemokine-dependent nature of allograft rejection, acceptance, and tolerance induction are presented as a basis for understanding the rationale for preclinical trials of chemokine receptor-targeted therapies currently underway in primate recipients of solid organ allografts.

Tolerance: is it achievable in pediatric solid organ transplantation?

Significant advances have been made in the understanding of allograft rejection. There is growing awareness that allograft acceptance, or tolerance, is also an active process rather than a passive absence of rejection. Mechanistic awareness of this process has spawned many preclinical strategies for the prevention of allograft rejection without the need for chronic immunosuppression. These therapies are currently entering clinical trials. This article reviews the prevailing therapies that hold promise for future clinical application. In particular, their application in children is discussed, as are biologic aspects of childhood immunity that may play a role in the success or failure of these strategies.