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Donor-reactive memory cells represent a barrier to long-term kidney graft survival. A better understanding of regulatory mechanisms that counterbalance alloreactive memory responses may help to identify patients with operational tolerance. This prospective study investigated the equilibrium between memory T-cell subsets and regulatory T or B cells (Tregs, Bregs) in peripheral blood of kidney transplant recipients with operational tolerance (N = 8), chronic rejection (N = 8), and different immunosuppressive treatment regimens (N = 81). Patients on hemodialysis and healthy individuals served as controls (N = 50). In addition, the expression of Treg- and Breg-associated molecule genes was analyzed. Patients with chronic rejection showed a disrupted memory T-cell composition with a significantly higher frequency of circulating CD8+ terminally differentiated effector memory (TEMRA) T cells than patients with operational tolerance, patients on hemodialysis, or healthy controls (P < 0.001). Low frequency of CD8+ TEMRA and high frequency of Tregs and transitional Bregs were found in operationally tolerant patients. Consequently, operationally tolerant patients showed, as compared to all other transplant recipients with different immunosuppressive regiments, the lowest ratios between CD8+ TEMRA T cells and Tregs or Bregs (for both P < 0.001). Moreover, a specific peripheral blood transcription pattern was found in operationally tolerant patients with an increased expression of Breg- and Treg-associated genes CD22 and FoxP3 and a decreased FcγRIIA/FcγRIIB transcript ratio (for all P < 0.001). In conclusion, monitoring the balance between circulating CD8+ TEMRA T cells and regulatory cell subsets and their transcripts may help to distinguish transplant recipients with operational tolerance from recipients at risk of graft loss. We show that a balance between effector mechanisms mediated by CD8 + TEMRA T cells and regulatory cell populations such as Bregs, Tregs, or naive T cells determines long-term kidney graft survival. Monitoring the balance between circulating CD8 + TEMRA T cells and regulatory cell subsets and their transcripts may help to distinguish transplant recipients with OT from recipients at risk of graft loss. Our study provides evidence in favor of regulatory mechanisms that counterbalance alloreactive memory immune responses and may encourage further investigations whether the ratio between CD8 + TEMRA T cells and Tregs or Bregs can help to safely guide minimization of immunosuppression in selected patients. Graphical Abstract [ABSTRACT FROM AUTHOR]

Natural Killer (NK) cells are innate immune cells that mediate antiviral and antitumor responses. NK cell activation and induction of effector functions are tightly regulated by the integration of activating and inhibitory receptors such as killer immunoglobulin-like receptors (KIR). KIR genes are characterized by a high degree of diversity due to presence or absence, gene copy number and allelic polymorphism. The aim of this study was to establish the distribution of KIR genes and genotypes, to infer the most common haplotypes in an admixed Colombian population and to compare these KIR gene frequencies with some Central and South American populations and worldwide. A total of 161 individuals from Medellin, Colombia were included in the study. Genomic DNA was used for KIR and HLA genotyping. We analyzed only KIR gene-content (presence or absence) based on PCR-SSO. The KIR genotype, most common haplotypes and combinations of KIR and HLA ligands frequencies were estimated according to the presence or absence of KIR and HLA genes. Dendrograms, principal component (PC) analysis and Heatmap analysis based on genetic distance were constructed to compare KIR gene frequencies among Central and South American, worldwide and Amerindian populations. The 16 KIR genes analyzed were distributed in 37 different genotypes and the 7 most frequent KIR inferred haplotypes. Importantly, we found three new genotypes not previously reported in any other ethnic group. Our genetic distance, PC and Heatmap analysis revealed marked differences in the distribution of KIR gene frequencies in the Medellin population compared to worldwide populations. These differences occurred mainly in the activating KIR isoforms, which are more frequent in our population, particularly KIR3DS1. Finally, we observed unique structural patterns of genotypes, which evidences the potential diversity and variability of this gene family in our population, and the need for exhaustive genetic studies to expand our understanding of the KIR gene complex in Colombian populations. [ABSTRACT FROM AUTHOR]

The mechanisms underlying maintenance of renal allografts in humans under minimal or conventional immunosuppression are poorly understood. There is evidence that CD4+ CD25+ regulatory T cells and clonal deletion, among other mechanisms of tolerance, could play a key role in clinical allograft survival. Twenty-four TCR-Vβ families were assessed in CD4+ CD25−, CD4+ CD25low and CD4+ CD25high T cells from patients with long-term renal allograft survival (LTS), patients exhibiting chronic rejection (ChrRx), patients on dialysis (Dial) and healthy controls (HC) by flow cytometry. LTS patients presented a higher variability in their TCR-Vβ repertoire, such decreased percentage of Vβ2+, Vβ8a+ and Vβ13+ in CD4+ CD25low and high compared with CD4+ CD25− subset and increased Vβ4 and Vβ7 families in CD4+ CD25high T cells exclusively. Additionally, LTS patients, particularly those that were not receiving calcineurin inhibitors (CNI), had increased percentages of CD4+ CD25high T cells when compared with Dial ( P < 0.05) and ChrRx ( P < 0.05) patients. Our results suggest that a differential expression of particular TCR-Vβ families and high levels of circulating CD4+ CD25high T cells in long-term surviving renal transplant patients could contribute to an active and specific state of immunologic suppression. However, the increase in this T cell subset with regulatory phenotype can be affected by CNI. [ABSTRACT FROM AUTHOR]

High serum sCD30 levels are associated with inflammatory disorders and poor outcome in renal transplantation. The contribution to these phenomena of transcripts and proteins related to CD30-activation and -cleavage is unknown. We assessed in peripheral blood of end-stage renal disease patients (ESRDP) transcripts of CD30-activation proteins CD30 and CD30L, CD30-cleavage proteins ADAM10 and ADAM17, and Th1- and Th2-type immunity-related factors t-bet and GATA3. Additionally, we evaluated the same transcripts and release of sCD30 and 32 cytokines after allogeneic and polyclonal T-cell activation. In peripheral blood, ESRDP showed increased levels of t-bet and GATA3 transcripts compared to healthy controls (HC) (both P < 0.01) whereas levels of CD30 , CD30L , ADAM10 and ADAM17 transcripts were similar. Polyclonal and allogeneic stimulation induced higher levels of CD30 transcripts in ESRDP than in HC (both P < 0.001). Principal component analysis (PCA) in allogeneic cultures of ESRDP identified two correlation clusters, one consisting of sCD30, the Th-1 cytokine IFN-γ, MIP-1α, RANTES, sIL-2Rα, MIP-1β, TNF-β, MDC, GM-CSF and IL-5, and another one consisting of CD30 and t-bet transcripts, IL-13 and proinflammatory proteins IP-10, IL-8, IL-1Rα and MCP-1. Reflecting an activated immune state, ESRDP exhibited after allostimulation upregulation of CD30 transcripts in T cells, which was associated with Th1 and proinflammatory responses. [ABSTRACT FROM AUTHOR]

Abstract: High serum levels of soluble CD30 (sCD30) are associated with poor renal allograft survival, and regulatory T cells (Tregs) influence allograft survival depending on CD30 signaling. However, how sCD30 modulates alloimmune responses remains poorly understood. We measured the level of Tregs and sCD30 in patients with end-stage renal failure (ESRF) and analyzed whether allo- or polyclonal stimulation of the patients’ T cells results in the expression and release of CD30. ESRF patients showed increased serum sCD30 levels and lower percentages of circulating Tregs as compared to healthy controls (HC) (p <0.001 and 0.024). Polyclonal and allogeneic stimulation resulted in higher expression of CD30, and after polyclonal stimulation, ESRF patients showed higher percentages of CD30-expressing T cells than HC (p <0.001). Compared to autologous stimulation, allogeneic stimulation induced significantly higher expression of CD30 on T cells of ESRF patients only. After polyclonal as well as allogeneic stimulation, an increased sCD30 content was found in culture supernatants of both ESRF patients and HC (p <0.001). Together with decreased Tregs, high serum sCD30 and increased induction of CD30 on T cells after polyclonal stimulation may explain exacerbated alloimmune responses and poor allograft survival in ESRF patients in whom immunosuppression is not able to control the alloimmune response. [Copyright &y& Elsevier]

Background: We recently demonstrated that donor-derived modified immune cells (MICs)-PBMCs that acquire immunosuppressive properties after a brief treatment-induced specific immunosuppression against the allogeneic donor when administered before kidney transplantation. We found up to a 68-fold increase in CD19 + CD24 hi CD38 hi transitional B lymphocytes compared with transplanted controls., Methods: Ten patients from a phase 1 clinical trial who had received MIC infusions before kidney transplantation were followed to post-transplant day 1080., Results: Patients treated with MICs had a favorable clinical course, showing no donor-specific human leukocyte antigen antibodies or acute rejections. The four patients who had received the highest dose of MICs 7 days before surgery and were on reduced immunosuppressive therapy showed an absence of in vitro lymphocyte reactivity against stimulatory donor blood cells, whereas reactivity against third party cells was preserved. In these patients, numbers of transitional B lymphocytes were 75-fold and seven-fold higher than in 12 long-term survivors on minimal immunosuppression and four operationally tolerant patients, respectively ( P <0.001 for both). In addition, we found significantly higher numbers of other regulatory B lymphocyte subsets and a gene expression signature suggestive of operational tolerance in three of four patients. In MIC-treated patients, in vitro lymphocyte reactivity against donor blood cells was restored after B lymphocyte depletion, suggesting a direct pathophysiologic role of regulatory B lymphocytes in donor-specific unresponsiveness., Conclusions: These results indicate that donor-specific immunosuppression after MIC infusion is long-lasting and associated with a striking increase in regulatory B lymphocytes. Donor-derived MICs appear to be an immunoregulatory cell population that when administered to recipients before transplantation, may exert a beneficial effect on kidney transplants., Clinical Trial Registry Name and Registration Number: MIC Cell Therapy for Individualized Immunosuppression in Living Donor Kidney Transplant Recipients (TOL-1), NCT02560220., (Copyright © 2022 by the American Society of Nephrology.)

A significant association between HFE gene mutations and the HLA-A*03-B*07 and HLA-A*29-B*44 haplotypes has been reported in the Spanish population. It has been proposed that these mutations are probably connected with Celtic and North African ancestry, respectively. We aimed to find the possible ancestral association between HLA alleles and haplotypes associated with the HFE gene (C282Y and H63D) mutations in 214 subjects from Antioquia, Colombia. These were 18 individuals with presumed hereditary hemochromatosis ("HH") and 196 controls. The HLA-B*07 allele was in linkage disequilibrium (LD) with C282Y, while HLA-A*23, A*29, HLA-B*44, and B*49 were in LD with H63D. Altogether, our results show that, although the H63D mutation is more common in the Antioquia population, it is not associated with any particular HLA haplotype, whereas the C282Y mutation is associated with HLA-A*03-B*07, this supporting a northern Spaniard ancestry.

Background: Membrane CD30 is an important costimulatory molecule for activated T lymphocytes, and serum level of soluble CD30 (sCD30) is considered a marker for predicting outcome in kidney transplantation., Methods: We investigated the kinetics of CD30 expression on CD4 and CD8 T-cell populations and the source of sCD30 during alloimmune responses in vitro. The effect of neutralizing antibodies against interferon (IFN)-γ and other cytokines on sCD30 release and the involvement of metalloproteinases ADAM10 and ADAM17/TACE that are responsible for sCD30 shedding were also assessed. Memory phenotypes and CD30 expression on allostimulated CD3 lymphocytes were evaluated in dialysis patients and matched controls., Results: Allogeneic stimulation resulted in conversion of naive responder cells to central memory CD4 cells (P<0.001 at 96 hr) and effector CD8 cells (P<0.01 at 120 hr), which was accompanied by increased CD30 expression. Release of sCD30 was attributed mainly to central memory cells, and neutralization of IFN-γ (P<0.001) and interleukin (IL)-2 (P<0.001) impaired the release of sCD30 during allostimulation but did not alter the levels of ADAM10 and ADAM17/TACE. CD30 expression was modulated in dialysis patients in a similar way as in healthy controls., Conclusions: Allostimulation results in the up-regulation of the T-cell activation marker CD30 on CD4 as well as CD8 memory T cells and increased release of sCD30 from these cells in an IFN-γ- and IL-2-dependent manner. These results may explain clinical findings on the suitability of sCD30 and IFN-γ- and IL-2-producing T cells for immune monitoring of kidney transplant recipients before and after transplantation.

Allospecific memory T cells are a barrier against long-term graft survival. Production of multiple cytokines by a single T cell is considered a sign of an active ongoing immune response, the presence of these polyfunctional cells has not been addressed in transplanted patients accordingly to graft outcome. Memory phenotype, based on the expression of CD45RO and CD27, and polyfunctional T cells were evaluated in long-term graft survival patients (LTS), short-term survival patients (STS), chronic rejection patients (ChrRx), dialysis patients (DIAL) and healthy controls (Ctrls). Memory T cells were quantified ex vivo, after allogeneic and anti-CD3 plus anti-CD28 stimulation, in cells proliferating or not to these stimuli. The percentages of cells producing IFNγ, IL-2 and/or TNFα after allogeneic stimulation and the memory phenotype of single cytokine producing cells were evaluated. Ex vivo CD8+CD45RO-CD27- effector cells were decreased in transplanted patients compared to non-transplanted individuals. After allogeneic stimulation, CD4+CD45RO+CD27+, central memory cells in LTS and CD4+CD45RO-CD27- effector cells in Dial were augmented compared to Ctrls and ChrRx, and CD8+CD45RO-CD27- effector cells were increased in ChrRx. There were no differences in the percentage of single cytokine producing cells among the groups. IFNγ+TNFα+CD4 and CD8 cells were detected in Ctrls, STS and ChrRx and no cells positive for the three cytokines were found. The phenotype of cytokine producing cells was mainly effector memory. Interestingly, in LTS there was an increase in effector cells producing IFNγ and IL-2. Changes in subpopulation distribution in patients with different outcomes may be a reflection of the graft acceptance or rejection status., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Dendritic cells, the most powerful antigen-presenting cells, are important for triggering of the immune responses to allo-antigens. However, they also play a fundamental role in the peripheral tolerance maintenance. Tolerance is enhanced by the presence on the dendritic cell surface of the inhibitor receptors ILT3 and ILT4. They recruit protein tyrosine-phosphatases to their ITIM domains and inhibit antigen-presenting cell activation, leading T cell hypo-responsivensess. Moreover, these receptors favor a bidirectional interaction with T-suppressor and T-regulator cells, generating an antigen-specific immunoregulator cascade, in which the dendritic cell behaves as a tolerogenic cell. In the current review, analysis is centered on the biology and behavior of the tolerogenic dendritic cells that express high levels of ILT3 and ILT4. Some molecular and genetics aspects of these receptors are discussed as well as their importance in the modulation of the allo-specific antigen immune response to transplants.

Introduction: Genetic characterization of the human leucocyte antigen (HLA) system has provided insights into mechanisms of susceptibility to diverse diseases and immunological phenomena during pregnancy, as well as providing evidence for compatibility in the selection of organ transplant donors and recipients., Objective: The HLA-A,-B,-DRB1 allele, genotype and haplotype frequencies were determined in deceased organ donors in Medellín, Colombia., Materials and Methods: The genotypes of 926 deceased donors were evaluated over a 17-year period (1989- 2006). HLA-A, HLA-B and HLA-DRB1 typing was performed by sequence specific primer-polymerase chain reaction (SSP-PCR). Maximum likelihood frequencies were estimated by the zipper version of expectation maximation algorithm. Hardy-Weinberg equilibrium were determined by an exact test analogous to Fishers test by using Markovs chain, and linkage disequilibrium between pairs of loci., Results: Twenty-two, 43 and 14 alleles were identified for HLA-A, -B and -DRB loci, respectively. The most frequent were A*02, A*24, B*35, and DRB1*04. A deficiency in the proportion of heterozygotes in HLA-A and B loci (p<0.01 and p<0.00001, respectively). The most frequent haplotypes were as follows: HLA-A*24, B*35 (7.7%) for HLA-A,-B; HLA-B*35, DRB1*04 (6.4%) for HLA-B,-DRB1 and HLA-A*24, DRB1*04 (8.9%) for HLA-A,-DRB1. For the 3 loci HLA-A,-B,-DRB1, the most frequent haplotypes were A*24, B*35, DRB1*04 (4.6%) and A*24, B*61, DRB1*04 (2.0%)., Conclusions: These results confirm the three-ethnic ancestry of the Medellin population. The predominance of Caucasian admixture differs from many other Latin-American populations and can serve as a reference for comparative studies of these populations as well as applications within the Medellin population.

The immune response elicited by an allogenic transplant usually leads to an effector response resulting in allograft rejection; however, some individuals maintain a long-term functioning transplant without signs of rejection (operational tolerance) even in the absence of immunosuppression. It has been suggested that the same mechanisms are responsible for tolerance to self-antigens and alloantigens. One of such mechanisms is immune regulation and several cell subsets with regulatory properties have been identified. Among them, the best characterized cell populations are the regulatory T cells (Treg). Although Treg in mice are CD4+CD25+, in humans the Treg phenotype is restricted to CD4 T cells with high expression of CD25 (CD25high) and Foxp3. Phenotypic and functional analysis of circulating regulatory or suppressor T cells in transplant patients may be useful for detection of operationally tolerant patients. Moreover, future in vitro manipulation of these cells with therapeutic purposes could lead to accomplish induction of in vivo tolerance in clinical transplantation. Herein, we review the experimental and clinical evidence for the role of regulatory cells in transplant biology.

Background: Patients with long-term functioning organ allografts may have developed different mechanisms that explain the lack of graft rejection. However, it is not known how these mechanisms interplay or whether one of them predominates in such situations., Methods: The authors analyzed the expression of T-cell surface molecules involved in alloantigen recognition, signal transduction, co-stimulation, and activation markers on circulating T cells from patients with normal kidney function 10 or more years after transplantation, short-term survival (1-4 years), and chronic rejection and from healthy adults. The percentage and the median fluorescent intensity of each marker were determined by flow cytometry. Proliferative response against specific and third-party donors and mitogenic stimulation were also determined., Results: Peripheral blood lymphocytes from patients with long-term surviving kidneys had decreased expression of T-cell receptor (TCR)-alphabeta (P < 0.01), CD3epsilon (P < 0.05), and CD3 zeta-chains (P < 0.001); diminished percentages of CD4(+)CD28(+) (P < 0.001) cells; and increased expression of CTLA-4(+) (P < 0.01) on CD3(+) cells. CD4(+)CD25(+)CD69(+) cells were also increased in long-term surviving patients. Long-term surviving patients had decreased donor-specific proliferative responses., Conclusions: The decreased expression of TCR-alphabeta and epsilon- and zeta-chains on circulating T cells of long-term surviving patients suggests that these cells may have defects in alloantigen recognition or signal transduction that may result in decreased numbers of T cells expressing co-stimulatory molecules and activation markers as well as a decreased specific proliferative response. The decrease in the percentage of CD28(+) cells and the increase in CD4(+)CD25(+)CD69(+) cells suggest that regulatory mechanisms of the immune response are still active in such patients.