Phase III clinical studies have shown that kidney transplant (KT) recipients treated with the costimulation blocker belatacept exhibited a better renal allograft function and lower donor‐specific ...anti‐HLA immunization when compared to recipients treated with calcineurin inhibitors (CNI). We analyzed B cell phenotype in KT recipients treated with belatacept and stable renal function (N = 13). Results were compared to those observed in stable patients treated with CNI (N = 12), or with chronic antibody‐mediated rejection (N = 5). Both transcriptional profile and phenotypic characterization of peripheral B cells were performed by real‐time polymerase chain reaction and flow cytometry, respectively. In belatacept group, the frequency and absolute number of transitional B cells as defined by both phenotypes: CD19+CD24hiCD38hi and CD19+IgDhiCD38hiCD27−, as well as naïve B cells were significantly higher compared with CNI group. B cell activating factor (BAFF) and BAFF receptor mRNA levels were significantly lower in belatacept group than in CNI group. These results show for the first time that belatacept influences B cell compartment by favoring the occurrence of transitional B cells with potential regulatory properties, as described in operational tolerant patients. This role may explain the lower alloimmunization rate observed in belatacept‐treated patients.
The authors report a B cell phenotype analysis in kidney transplant recipients who have stable renal function on belatacept maintenance immunosuppression, and show that belatacept influences the B cell compartment by favoring the occurrence of transitional B cells as described in operationally tolerant patients. (Also see article by Kirk et al on page 1142.)
Exploiting the antitumor effect of natural killer (NK) cells has regained interest in light of data from preclinical and clinical work on the potential of alloreactive NK cells. Multiple myeloma (MM) ...and chronic lymphocytic leukemia (CLL) represent the two most prevalent adult hematological malignancies in the western hemisphere. To evaluate the role of NK cells in the immune surveillance and their therapeutic potential for CLL and MM, tumor cell susceptibility to NK-mediated killing was investigated. Results show relative resistance of tumor cells from CLL as well as MM (73 and 70% of the patients, respectively) to NK-mediated killing. To gain insight into molecular mechanisms of this resistance, the expression of the tolerogenic HLA-G molecule in CLL and MM and its relevance to susceptibility to NK-mediated killing were investigated. HLA-G transcript was found in tumor cells from 89% (n=19) of CLL and 100% (n=9) of MM patients examined. HLA-G1 surface expression was observed in CLL and was very low or undetectable in MM. Notably, blocking of HLA-G1 with specific antibody on CLL samples increased their susceptibility to NK-mediated killing, demonstrating that HLA-G participates in protecting CLL cells from NK-mediated killing and may thus contribute to their immune escape in vivo.
HLA-G was described as a molecule inhibiting NK and T cells functions through its receptor, ILT2. However, most functional studies of HLA-G were so far performed on heterogeneous immune populations ...and regardless of ILT2 expression. This may lead to an underestimation of the effect of HLA-G. Thus, considering the immune subpopulations sensitive to HLA-G remained an important issue in the field. Here we present a new cytometry assay to evaluate HLA-G effects on both NK and CD8+ T cell cytotoxic functions.
Using flow cytometry allows for the comparison of HLA-G function on multiple subsets and multiple functions in the same time. In particular, we sharpen the analysis by specifically studying the immune subpopulations expressing HLA-G receptor ILT2. We focused our work on: IFN-gamma production and cytotoxicity (CD107a expression) by CD8+ T cells and NK cells expressing or not ILT2. We compared the expression of these markers in presence of target cells, expressing or not HLA-G1, and added a blocking antibody to reverse HLA-G inhibition.
This new method allows for the discrimination of cell subsets responding and non-responding to HLA-G1 in one tube. We confirm that HLA-G-specifically inhibits the ILT2+ CD8+ T cell and ILT2+ NK cell subsets but not ILT2-negative ones. By blocking HLA-G/ILT2 interaction using an anti-ILT2 antibody we restored the cytotoxicity level, corroborating the specific inhibition of HLA-G1. We believe that our methodology enables to investigate HLA-G immune functions easily and finely towards other immune cell lineages or expressing other receptors, and might be applied in several pathological contexts, such as cancer and transplantation.
HLA-G is a nonclassical MHC class I molecule that plays a major role in maternal-fetal tolerance. Four membrane-bound (HLA-G1 to -G4) and two soluble (HLA-G5, and -G6) proteins are generated by ...alternative splicing. Only HLA-G1 has been extensively studied in terms of both expression and function. We provide evidence here that HLA-G2, -G3, and -G4 truncated isoforms reach the cell surface of transfected cells, as endoglycosidase H-sensitive glycoproteins, after a 2-h chase period. Moreover, cytotoxicity experiments show that these transfected cells are protected from the lytic activity of both innate (NK cells) and acquired (CTL) effectors. These findings highlight the immunomodulatory role that HLA-G2, -G3, and -G4 proteins will assume during physiologic or pathologic processes in which HLA-G1 expression is altered.
We recently reported that the nonclassical HLA class I molecule HLA-G was expressed in the endomyocardial biopsies and sera of 16% of heart transplant patients studied. The aim of the present report ...is to identify cells that may be responsible for HLA-G protein expression during the allogeneic reaction. Carrying out mixed lymphocyte cultures in which the responder cell population was depleted either in CD4+or CD8+T cells, we found that soluble HLA-G5 protein but not the membrane-bound HLA-G isoform was secreted by allo-specific CD4+T cells from the responder population, which suppressed the allogeneic proliferative T cell response. This inhibition may be reversed by adding the anti-HLA-G 87G antibody to a mixed lymphocyte culture. That may indicate a previously uncharacterized regulatory mechanism of CD4+T cell proliferative response.
Human leukocyte antigen‐G (HLA‐G), a nonclassical HLA class I protein, promotes immune tolerance of solid‐organ allografts, yet its role in lung transplantation (LTx) is unknown. We examined the ...expression of HLA‐G in lung allografts through immunohistochemistry by a cross‐sectional study of 64 LTx recipients, classified into four groups (stable patients, acute rejection AR, bronchiolitis obliterans syndrome BOS and symptomatic viral shedders). A marked expression of HLA‐G in bronchial epithelial cells (BEC) was frequently observed in stable recipients (n = 18/35 51%), but not in patients with AR (n = 14) or with BOS (n = 8). HLA‐G was also expressed by 4 of 7 symptomatic viral shedders. In addition, HLA‐G‐positive patients from the stable group (n = 35) experienced lower incidence of resistant AR and/or BOS during long‐term follow‐up, as compared with their HLA‐G‐negative counterparts. Finally, in vitro data showed that interferon‐γ, a cytokine present in lung allograft microenvironment, upregulated HLA‐G mRNA and protein expression in primary cultured human BEC. We conclude that HLA‐G expression in the bronchial epithelium of lung allograft is elevated in some LTx recipients in association with their functional stability, suggesting a potential role of HLA‐G as a tolerance marker.
HLA‐G expression in the bronchial epithelium of lung allograft is elevated in some LTx recipients in association with their functional stability.
HLA-G: from biology to clinical benefits Carosella, Edgardo D; Moreau, Philippe; LeMaoult, Joël ...
Trends in immunology,
03/2008, Letnik:
29, Številka:
3
Journal Article
Recenzirano
The relevance of the nonclassical human leukocyte antigen (HLA) class I molecule HLA-G in human physiological and pathological contexts has been the center of intense investigation. In light of the ...recent advances, we report here the clinical implications of HLA-G as a tolerogenic molecule promoting uterine implantation of the embryo or acceptance of solid allografts while allowing the evasion of tumors or viruses from the immune response. These recent findings are important in terms of clinical benefits at both diagnostic and therapeutic levels.
Human leukocyte antigen G (HLA‐G) expression is thought to be associated with a tolerance state following solid organ transplantation. In a lung transplant (LTx) recipient cohort, we assessed (1) the ...role of HLA‐G expression as a predictor of graft acceptance, and (2) the relationship between (i) graft and peripheral HLA‐G expression, (ii) HLA‐G expression and humoral immunity and (iii) HLA‐G expression and lung microenvironment. We prospectively enrolled 63 LTx recipients (median follow‐up 3.26 years min: 0.44–max: 5.03). At 3 and 12 months post‐LTx, we analyzed graft HLA‐G expression by immunohistochemistry, plasma soluble HLA‐G (sHLA‐G) level by enzyme–linked immunosorbent assay, bronchoalveolar lavage fluid (BALF) levels of cytokines involved in chronic lung allograft dysfunction (CLAD) and anti‐HLA antibodies (Abs) in serum. In a time‐dependent Cox model, lung HLA‐G expression had a protective effect on CLAD occurrence (hazard ratio: 0.13 0.03–0.58; p = 0.008). The same results were found when computing 3‐month and 1‐year conditional freedom from CLAD (p = 0.03 and 0.04, respectively log‐rank test). Presence of anti‐HLA Abs was inversely associated with graft HLA‐G expression (p = 0.02). Increased BALF level of transforming growth factor‐β was associated with high plasma sHLA‐G level (p = 0.02). In conclusion, early graft HLA‐G expression in LTx recipients with a stable condition was associated with graft acceptance in the long term.
Early graft HLA‐G expression in lung transplant recipients with a stable condition is associated with graft acceptance in the long‐term follow‐up.
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