Comparison and immunobiological characterization of retinoic acid inducible gene-I-like receptor expression in mesenchymal stromal cells.

Due to their immunomodulatory and regenerative properties, Mesenchymal stromal cells (MSC) have generated major interests in several clinical settings including transplantation and inflammatory diseases. MSC functions can be influenced by their tissue origin. Their microenvironment strongly affects their biology notably through TLR sensing. In this study, we show that MSC isolated from four different sources express another type of cytosolic pathogen recognition receptors known as retinoic acid inducible gene-I (RIG-I)-like receptors (RLR). RLR activation in MSC induces the production of Type I IFN (IFN-ß) and Type III IFN (IFN-λ1). The highest producers are adipose tissue(AT)-MSC. We further show that Interferon production is induced through TBK1/IKK-ε signaling and IRF7 phosphorylation. Depending on MSC source, the knockdown of TLR3 and/or RIG-I decreases the MSC response to RLR ligand poly(I:C)/Lyovec. Among the different MSC types, AT-MSCs display the highest sensitivity to viral stimuli as shown by the alteration of their viability after prolonged stimulation. Our work indicates that this could be linked to an increase of pro-apoptotic Noxa expression. Finally, the expression of IDO1 and LIF upon RLR activation indicate the increase of MSC immunomodulatory potential, especially in AT-MSCs. Altogether, these data should be considered when designing MSC-based therapy in clinical settings where inflammation or infection are present.

Human leucocyte antigen (HLA) class I and II typing in Belgian multiple sclerosis patients.

This is one of the first studies to compare the frequencies of different human leucocyte antigen (HLA) class I and II alleles and haplotype HLA-DRB1*15-DQB1*06 in a cohort of 119 patients with multiple sclerosis (MS) and a cohort of 124 healthy controls in Belgium. An association with MS was found for the HLA-DRB1*15 (odds ratio [OR] 2.60 [95% confidence interval (CI) 1.51-4.50]) and HLA-DQB1*06 (OR 1.97 [95% CI 1.18-3.29]) alleles, and for haplotype DRB1*15-DQB1*06 (OR 2.63 [95% CI 1.52-4.56]). The HLA-B*07 allele also tended to be more frequent in MS patients (OR 1.46 [95% CI 0.80-2.65]) and more frequent among MS patients with than in those without the HLA-DRB1*15 allele (26/54 [48.1%] versus 6/65 [9.2%]; p value <0.0001). Other alleles were underrepresented in MS patients, such as the HLA-DRB1*07 (OR 0.39 [95% CI 0.21-0.73]) and HLA-A*02 (OR 0.56 [95% CI 0.34-0.94]), showing a protective role against the disease. The HLA-B*44 (OR 0.58 [95% CI 0.31-1.09]) and HLA-DRB1*04 (OR 0.75 [95% CI 0.42-1.34]) alleles tended to be less frequent in MS patients. Altogether, the significant results observed in this population are in line with those from other countries and confirm that propensity to MS can be due to a complex presence of various HLA class I and class II alleles.

Human hepatic stellate cells and inflammation: A regulated cytokine network balance.

AIM: Uncertainty about the safety of cell therapy continues to be a major challenge to the medical community. Inflammation and the associated immune response represent a major safety concern hampering the development of long-term clinical therapy. In vivo interactions between the cell graft and the host immune system are mediated by functional environmental sensors and stressors that play significant roles in the immunobiology of the graft. Within this context, human liver stellate cells (HSC) demonstrated marked immunological plasticity that has main importance for future liver cell therapy application. METHODS: By using qPCR technique, we established the cytokine gene expression profile of HSCs and investigated the effect of an inflammatory environment on the immunobiology of HSCs. RESULTS AND DISCUSSION: HSCs present a specific immunological profile as demonstrated by the expression and modulation of major immunological cytokines. Under constitutive conditions, the cytokine pattern expressed by HSCs was characterized by the high expression of IL-6. Inflammation critically modulated the expression of major immunological cytokines. As evidenced by the induction of the expression of several inflammatory genes, HSCs acquire a pro-inflammatory profile that ultimately might have critical implications for their immunological shape. CONCLUSION: These new observations have to be taken into account in any future liver cell therapy application based on the use of HSCs.

Mesenchymal stromal cells from the foreskin: Tissue isolation, cell characterization and immunobiological properties.

BACKGROUND AIMS: Because of their self-renewal capacity, multilineage potential and immunomodulatory properties, MSCs are an attractive tool for cell-based immunotherapy strategies. Foreskin, considered as a biological waste material, has been shown to be a reservoir of therapeutic cells. METHODS: MSCs were isolated from different foreskin samples, maintained under in vitro culture and defined according to the International Society for Cellular Therapy (ISCT) criteria. We subsequently determined their main cell characteristics as well as their immunobiological properties. The following parameters were determined: (i) morphology and phenotype, (ii) proliferative and clonogenic potentials, (iii) tri-lineage differentiation ability, (iv) immunological profile, (v) immunomodulatory properties and (vi) protein and messenger RNA expression/secretion profile of immunoregulatory cytokines/factors as well as the pattern of toll-like receptors (TLRs). By using a pro-inflammatory cytokine cocktail, we also evaluated the influence of an inflammatory environment on their biology. RESULTS: With a typical fibroblast-like morphology and an ISCT-compliant phenotype, foreskin-MSCs (FSK-MSCs) were highly proliferative and had a great clonogenic potential. They displayed multilineage capacities and interesting immunomodulatory properties. Of importance, FSK-MSCs were not immunogenetic and were further able to inhibit T-cell proliferation. We showed that several immunoregulatory cytokines and factors might be potentially involved in FSK-MSC immunomodulation with particular attention to hepatocyte growth factor and interleukin-11. Moreover, FSK-MSCs expressed several TLRs and were sensitive to the inflammatory environment by properly adjusting their profile and fate. CONCLUSIONS: Foreskin represents a new alternative source for MSCs that is compliant with ISCT criteria. Their unique immunobiological properties allow consideration of FSK-MSCs as a valuable tolerogenic product for cell-based immunotherapy.

The Immunomodulatory Potential of Mesenchymal Stromal Cells: A Story of a Regulatory Network.

Mesenchymal stromal cells (MSCs) have recently been the subject of great interest in the fields of regenerative medicine and immunotherapy due to their unique biological properties. In particular, MSCs possess immunoregulatory properties that can modulate immune as well as inflammatory responses. Although there are many studies about MSC immunomodulation, several complex and conflicting mechanisms have been reported. Herein, we aim to review these mechanisms and identify a link between these pathways. We focus on human studies in which bone marrow-derived MSCs and T cells were investigated. We propose that MSC-induced immunomodulation exists as a network where converging regulatory pathways compete to establish a tolerogenic state. As interleukin-10 seems to play a central role in this network, we also discuss the relationship between this cytokine and other regulatory factors in the context of immunomodulation.

Mesenchymal stromal cells and immunomodulation: A gathering of regulatory immune cells.

Because of their well-recognized immunomodulatory properties, mesenchymal stromal cells (MSCs) represent an attractive cell population for therapeutic purposes. In particular, there is growing interest in the use of MSCs as cellular immunotherapeutics for tolerance induction in allogeneic transplantations and the treatment of autoimmune diseases. However, multiple mechanisms have been identified to mediate the immunomodulatory effects of MSCs, sometimes with several ambiguities and inconsistencies. Although published studies have mainly reported the role of soluble factors, we believe that a sizeable cellular component plays a critical role in MSC immunomodulation. We refer to these cells as regulatory immune cells, which are generated from both the innate and adaptive responses after co-culture with MSCs. In this review, we discuss the nature and role of these immune regulatory cells as well as the role of different mediators, and, in particular, regulatory immune cell induction by MSCs through interleukin-10. Once induced, immune regulatory cells accumulate and converge their regulatory pathways to create a tolerogenic environment conducive for immunomodulation. Thus, a better understanding of these regulatory immune cells, in terms of how they can be optimally manipulated and induced, would be suitable for improving MSC-based immunomodulatory therapeutic strategies.

Bone Marrow Mesenchymal Stromal Cells Induce Proliferative, Cytokinic and Molecular Changes During the T Cell Response: The Importance of the IL-10/CD210 Axis.

BACKGROUND: Bone marrow mesenchymal stromal cells (BM-MSCs) display immunomodulatory features, representing a promising tool for cell-based therapies. However, the mechanisms used by MSCs to regulate T cell fate remain unclear. AIMS: We investigated the potential of BM-MSCs to modulate T cell activation, proliferation, cytokine secretion and immunophenotype. MATERIALS AND METHODS: T cells were co-cultured with BM-MSCs to assess their immunomodulatory impact. T cell characterization was performed using cell tracing, ELISA, intracellular and surface staining, flow cytometry analysis and qPCR. RESULTS: The activation and proliferation of T cells were downregulated during coculture with BM-MSCs. We also observed that BM-MSCs upregulated IL-10 secretion as well as the expression of its receptor CD210 on T cells, thus creating a loop favoring the expansion of IL-10-producing T cells. IL-10 neutralization restored T cell proliferation, demonstrating that IL-10 is functionally relevant during immunomodulation. Moreover, BM-MSCs differently modulated CD4 and CD8 T-cell immunophenotype by inducing broad changes in their molecular pattern. CONCLUSIONS: We provide a comprehensive functional and molecular characterization of T cells that are immunomodulated by BM-MSCs. Indeed, a better understanding of the immunological interplay between T cells and MSCs will facilitate the development of new efficient approaches to improve cell-based immune therapies.

Influence of inflammation on the immunological profile of adult-derived human liver mesenchymal stromal cells and stellate cells.

BACKGROUND AIMS: Stem cell therapy for liver diseases has recently emerged as a promising alternative to liver transplantation. Eligible cells should have an appropriate immunophenotype. The aim of the present study was to define the immunological profile of two human liver-derived mesenchymal stromal cell populations, namely, stem cells (ADHLSC) and hepatic stellate cells (HSC). METHODS: The study was conducted under normal and inflammatory conditions with the use of human bone marrow mesenchymal stromal cells (BM-MSC) as reference. RESULTS: Like BM-MSC and ADHLSC, HSC were negative for hematopoietic (CD45) and endothelial (CD34) markers but positive for stromal markers. All cell types were constitutively positive for HLA class I and negative for human leukocyte antigen (HLA) class II and co-stimulatory molecules (CD80, CD86, CD134 and CD252). Inflammation induced the expression of CD40 in all cell types, but the highest values were observed on HSCs; high CD252 expression was only observed on HSC as compared with ADHLSC and BM-MSC. The expression of various adhesion molecules (CD54, CD58, CD106 and CD166) was dissimilar in these three cell types and was differentially influenced by inflammation as well. ADHLSC and HSC constitutively expressed the immunosuppressive molecule HLA-G, whereas CD274 expression was induced by inflammation, as in the case of BM-MSC. Moreover, all cell types expressed the two major natural killer ligands CD112 and CD115. CONCLUSIONS: Toll-like receptors (TLR) 1, 3, 4 and 6 messenger RNA was expressed by both cell types, whereas TLR 2, 5, 7, 9 and 10 were only expressed by ADHLSC. Inflammation increased the expression of TLR 2 and 3 by ADHLSC and HSC. Finally, both liver-derived cell types were immunosuppressive because they inhibited the proliferation of mitogen-activated T cells.

Impact of different mesenchymal stromal cell types on T-cell activation, proliferation and migration.

Mesenchymal stromal cells (MSCs) isolated from different tissue sources may present distinct immunomodulatory profiles. As lymphocyte responses are a combination of several distinct steps, we evaluated and compared the impact of MSCs from different sources on the activation, proliferation and migration of T-cells. We demonstrated that tissue-derived MSCs have important immunomodulatory effects. AT-MSCs induced potent anti-proliferative and anti-inflammatory (IFN-γ downregulation) effects and differentially modulated several T-cell activation markers (CD23, CD26, CD45, and CD69). Among all the MSC types tested, only AT-MSCs induced significant downregulation of CD26 and CD45 expression. Of importance, AT-MSCs maintained a sustained expression of CD69. AT-MSCs, particularly following exposure to an inflammatory environment, promoted the migration of lymphocytes into their surrounding environment. The AT-MSCs may increase recruitment of T lymphocytes by upregulation of IL-8 and CCL5 secretion. Following their migration, T-cells interact with MSCs, which can impair lymphocyte proliferation and activation depending on their origin. Inflammatory T-cells appeared to be progressively suppressed, which may lead to a population of lymphocytes with a regulatory phenotype. These findings are relevant, as they increase our understanding of the different immunomodulatory effect of MSCs as well as their behavior in an inflammatory environment.

Immune-related antigens, surface molecules and regulatory factors in human-derived mesenchymal stromal cells: the expression and impact of inflammatory priming.

Based on their ability to regulate immune responses, MSCs are considered to be potential candidates for managing immune-mediated diseases in the context of immune therapy. AT and WJ are considered valuable alternatives for BM as a source of MSCs. A detailed and comparative characterization of the immunological profile of MSCs derived from different sources, as well as an understanding of their responsiveness under certain circumstances, such as inflammation, is required to facilitate efficient and well-designed clinical studies. Flow cytometric analyses revealed clear differences among MSC types concerning the expression of the endothelial (e.g., CD31, CD34, CD144 and CD309) and stromal (e.g., CD90 and CD105) associated markers. Regardless of their source, MSCs did not express any of the known hematopoietic markers. All MSCs were uniformly positive for HLA-ABC and lacked the expression of HLA-DR and the co-stimulatory molecules (e.g., CD40, CD80, CD86, CD134 and CD252) required for full T-cell activation. Tissue-specific MSCs presented a modulated expression of cell adhesion molecules that is important for their cellular interactions. MSCs exhibited several surface (e.g., CD73, HLA-G, HO-1 and CD274) and soluble (e.g., HGF, PGE2 and IGFBP-3) immunoregulatory molecules. According to these immunological profiles, the present work provides evidence that the source from which MSCs are derived is important for the design of MSC-based immunointervention approaches. In light of these observations, we may suggest that WJ-MSCs appear to be the most attractive cell population to use in immune cellular therapy when immunosuppressive action is required.

Characterization and functionality of the CD200-CD200R system during mesenchymal stromal cell interactions with T-lymphocytes.

Mesenchymal stromal cells (MSCs) possess a specific immunological profile that makes them potentially useful for immune-based therapies. Adipose tissue (AT) and Wharton's jelly (WJ) are considered to be valuable alternatives to bone marrow (BM) as sources of MSCs. These MSCs exhibit strong immunomodulatory properties that affect lymphocyte responses. The CD200/CD200R axis has been reported to be important in regulating the immune responses. Engagement of CD200R by CD200 initiates an inhibitory pathway that displays immunosuppressive effects. Because the CD200/CD200R axis is involved in immunoregulation, we investigated the expression and role of this ligand/receptor pair in MSCs and T-lymphocytes during co-culture. CD200 is differently expressed and modulated on MSCs depending on the tissue of origin and the culture conditions. Among the different MSC sources, WJ-MSCs express CD200 in the greatest proportion. This high constitutive CD200 expression may represent a distinctive marker for WJ-MSCs. A pro-inflammatory environment and IFN-γ in particular induce an increase in CD200 expression by BM-MSCs. In T-lymphocytes, CD200R and CD200 are differently distributed between the CD4(+) and CD8(+) T-cell subsets. During co-culture, blocking CD200-CD200R interactions does not prevent MSC-mediated inhibition of lymphocyte proliferation. However, depending on their origin, MSCs are able to modulate the expression of both CD200 and CD200R on some T-cells. Further study is required to understand the function of CD200 expression by nonmyeloid cells such MSCs and the significance of CD200 and C200R expression by T-cells. The findings presented here support bidirectional communication between MSCs and T-lymphocytes. Understanding the role of this ligand-receptor pair during co-culture will improve and increase the clinical use of MSCs.

Posttransplant major histocompatibility complex class I chain-related gene A antibodies and long-term graft outcomes in a multicenter cohort of 779 kidney transplant recipients.

BACKGROUND: The impact of major histocompatibility class I chain-related A (MICA) antibodies on renal graft outcomes is unclear. The goal of this work was to assess the impact of posttransplant MICA antibodies, assayed at 1 year, with two commercially available kits, on long-term renal graft outcomes. METHODS: We retrospectively tested sera from 779 kidney transplant recipients with two single-antigen flow bead assays 1 year after transplantation. Samples were considered positive for MICA if they were positive in both tests or positive for MICA specificities that were present in one kit only. The main outcome was 4-year death-censored graft survival. RESULTS: The prevalence of MICA antibodies was 5.4% at 1 year. MICA+ patients were more frequently human leukocyte antigen (HLA) sensitized and regrafted. Four-year death-censored graft survival was not different between MICA+ and MICA- patients (97% vs. 94%, P=0.28). By Cox multivariate analysis, independent risk factors for graft loss were as follows: number of HLA DR mismatches, acute rejection within the first year posttransplantation, 1-year serum creatinine, and the presence of HLA antibodies at 1 year, but not the presence of MICA antibodies. CONCLUSIONS: These data do not support an independent pathogenic role for MICA in long-term renal graft injury and question the interest of posttransplant monitoring of MICA antibodies with single-antigen flow bead assays currently available.

Inflammation and Toll-like receptor ligation differentially affect the osteogenic potential of human mesenchymal stromal cells depending on their tissue origin.

Mesenchymal stromal cells (MSCs) can be isolated not only from bone marrow (BM) but also from other tissues, including adipose tissue (AT) and umbilical cord Wharton's Jelly (WJ). Thanks to their ability to differentiate into various cell types, MSC are considered attractive candidates for cell-based regenerative therapy. In degenerative clinical settings, inflammation or infection is often involved. In the present work, we hypothesized that an inflammatory environment and/or Toll-like receptor (TLR) ligation could affect the MSC differentiation potential. MSC were isolated from BM, AT, and WJ. Inflammation was mimicked by a cytokine cocktail, and TLR activation was induced through TLR3 and TLR4 ligation. Osteogenesis was chosen as a model for differentiation. Osteogenic parameters were evaluated by measuring Ca2+ deposits and alkaline phosphatase (ALP) activity at day 7, 14, and 21 of the culture in an osteogenic medium. Our results show that WJ-MSC exhibit a much lower osteogenic potential than the other two MSC types. However, inflammation was able to strongly increase the osteogenic differentiation of WJ-MSC as calcification, and ALP activity appeared as early as day 7. However, this latter enzymatic activity remained much lower than that disclosed by BM-MSC. TLR3 or TLR4 triggering increased the osteogenesis in AT- and, to lesser extent, in BM-MSC. In conclusion, WJ-MSC constitutively disclose a lower osteogenic potential as compared with BM and AT-MSC, which is not affected by TLR triggering but is strongly increased by inflammation, then reaching the level of BM-MSC. These observations suggest that WJ-MSC could constitute an alternative of BM-MSC for bone regenerative applications, as WJ is an easy access source of large amounts of MSC that can effectively differentiate into osteoblasts in an inflammatory setting.

The source of human mesenchymal stromal cells influences their TLR profile as well as their functional properties.

Mesenchymal stromal cells (MSC) can be expanded from different sources. We compared the influence of inflammation and TLR ligation on the phenotype and function of MSC derived from bone marrow (BM), adipose tissue (AT), and Wharton's jelly (WJ). WJ-MSC were featured by a lack of TLR4 expression. While inflammation upregulated TLR3 in all three MSC types, TLR4 upregulation was observed only on BM-MSC. TLR ligation increased the production of inflammatory cytokines in BM- and AT-MSC but not in WJ-MSC and augmented anti-inflammatory cytokines in AT-MSC. Although inflammation increased in all MSC types the secretion of inflammatory cytokines, additional TLR triggering did not have further effect on WJ-MSC. The immunosuppressive potential of WJ-MSC on MLR was affected neither by inflammation nor by TLR triggering. This resistance was related to an overproduction of HGF. These data indicate that MSC source could be of importance while designing immunomodulating cell therapy in transplantation.

Bortezomib: a new player in pre- and post-transplant desensitization?

Several desensitization strategies have been investigated for the reversal of acute antibody-mediated rejection or for the removal of preformed anti-HLA antibodies, with the aim to promote access to renal transplantation. Today, their success appears limited or incomplete. Bortezomib, a selective inhibitor of the 26S proteasome, which is largely used in the treatment of multiple myeloma, could be a novel promising desensitizing agent. Its mechanism of action and preliminary clinical use in renal transplantation is reviewed here.

Adipose-tissue-derived and Wharton's jelly-derived mesenchymal stromal cells suppress lymphocyte responses by secreting leukemia inhibitory factor.

Mesenchymal stromal cells (MSCs) possess immunomodulatory functions and have been proposed as a tool for managing or preventing graft-versus-host disease. Recently, adipose tissue (AT) and Wharton's jelly (WJ) have been reported as potential alternative MSC sources to bone marrow (BM). In this study, we investigated the capacity of MSCs derived from AT and WJ to modulate lymphocyte proliferation as well as their impact on regulatory T-cells. We also evaluated MSC expression of leukemia inhibitory factor and the role of this molecule in the mechanism of MSC-mediated inhibition. We demonstrated that WJ- and AT-MSCs induced a dose-dependent inhibition of T-cell proliferation regardless of the stimuli used to activate T-cells. WJ- and AT-MSCs were more potent than BM-MSCs in suppressing lymphocyte responses, and they mediated this effect by secreting high levels of leukemia inhibitory factor. We also observed that WJ- and AT-MSCs maintained and promoted the expansion of regulatory T-cells independently of the MSC/T-cell ratio. Because human WJ and AT contain MSCs with potent immunomodulatory capacities, they could represent an alternative to BM. Using WJ- and AT-MSCs in clinical therapies, such as the prevention and/or reduction of graft-versus-host disease and in the treatment of autoimmune diseases, is particularly promising. Further characterization of MSC physiological functions will increase the safety and efficacy of their use in clinical settings.

Mesenchymal stromal cells use PGE2 to modulate activation and proliferation of lymphocyte subsets: Combined comparison of adipose tissue, Wharton's Jelly and bone marrow sources.

Due to their immunomodulatory properties, adipose tissue (AT) and Wharton's Jelly (WJ) constitute valuable alternatives to BM as sources of MSCs for managing graft-versus-host disease. To ensure the efficiency of AT- and WJ-MSCs implies the characterization of their immunomodulatory functions in comparison to those of BM. In this study, we investigated the capacity of AT- and WJ-MSCs to modulate lymphocyte reactions in response to different stimuli as well as the specificity of this immunomodulation. AT- and WJ-MSC displayed potent immunosuppressive effects on lymphocyte responses in a dose-dependent manner. These effects included the prevention of lymphocyte activation as well as the suppression of T-cell proliferation regardless of the stimuli used to activate lymphocytes. These effects were mediated through the expression of COX1/COX2 enzymes and by the production of PGE2. CD4(+) and CD8(+) T-lymphocytes were equally targeted by MSCs demonstrating that the immunomodulation was not restricted to a specific T-cell subpopulation.

Modulated expression of adhesion molecules and galectin-1: role during mesenchymal stromal cell immunoregulatory functions.

OBJECTIVE: As mesenchymal stromal cells (MSCs) have been proposed as a tool for management or prevention of graft-vs-host disease, we investigated their immunoregulatory properties, their expression of adhesion molecules and galectin-1, and the impact of environment context on these functions. MATERIALS AND METHODS: The effects of MSCs on T-cell proliferation were analyzed using carboxyfluorescein diacetate N-succinimidyl ester labeling. We evaluated the expression of adhesion molecules and galectin-1 by MSCs and the impact of an inflammatory or infectious environment on these expressions. Using neutralizing antibodies against adhesion molecules and a galectin-1 inhibitor, we assessed the role of these molecules in MSC functions. RESULTS: MSCs inhibition of T-cell proliferation depended on MSC concentrations, cell contact, and culture environment. Expression of adhesion molecules and secretion of galectin-1 by MSCs are tightly regulated. Coculture with activated T cells upregulated expression of CD54 (intercellular adhesion molecule 1) and CD58 (lymphocyte function-associated antigen 3) and secretion of galectin-1 by MSCs. Interestingly, in an inflammatory or infectious environment, expression of adhesion molecules and galectin-1 by MSCs was differentially modulated. Furthermore, blocking galectin-1 activity prevented the suppressive potential of MSCs. Neutralization of adhesion molecule activity had no effect on MSC inhibition. CONCLUSION: Galectin-1 plays an important role in MSC immunoregulatory functions, which are depending on cell environment. The present study provides new insights concerning MSC physiology and will increase the safety and efficiency of MSCs in clinical settings.

Major histocompatibility complex class 1 chain-related antigen a antibodies: sensitizing events and impact on renal graft outcomes.

BACKGROUND: Major histocompatibility complex class 1 chain-related antigen A (MICA) antibodies (Abs) have been associated with renal graft loss in one large cohort. The triggering factors for MICA Abs and their autologous or allogeneic specificity have not been well defined. More data on the impact of MICA on renal grafts outcome are needed. METHODS: We tested sera from 494 controls and 597 patients with chronic kidney disease (CKD) for MICA using Luminex. Forty CKD MICA+ patients were genotyped for MICA alleles to determine their auto- or allospecificity. We compared MICA+ with MICA- renal transplant recipients with regard to acute rejection episodes and long-term survival. RESULTS: Blood transfusions, previous transplantation, and more than two pregnancies were independent risk factors for the presence of MICA Abs, as were CKD stage V status and male gender. Among the 40 genotyped patients, allo-Abs alone were present in 32 patients, both auto- and allo-Abs in 4 patients, and auto-Abs alone in 4 patients. When we compared MICA+ with MICA- patients, the incidence of acute rejection episodes during the first year (10.2% vs. 12.8%), as well as 1-year creatinine and proteinuria, were similar in both groups. At 10 years, actuarial patient (97.8% vs. 87.6%) and overall graft survival (76% vs. 72%) were similar between MICA+ and MICA- patients. CONCLUSIONS: In summary, (1) sensitizing events for MICA Abs are the same as for human leukocyte antigen Abs; (2) MICA Abs did not adversely affect renal graft outcomes in our cohort.

Mesenchymal stromal cells promote or suppress the proliferation of T lymphocytes from cord blood and peripheral blood: the importance of low cell ratio and role of interleukin-6.

BACKGROUND AIMS: Mesenchymal stromal cells (MSC) have been shown to possess immunomodulatory functions and proposed as a tool for managing or preventing graft-versus-host disease (GvHD) as well as promoting clinical transplantation tolerance. We investigated the capacity of human bone marrow (BM) MSC to modulate the proliferation of T cells obtained from peripheral blood (PB) and umbilical cord blood (CB). We addressed the importance of the MSC:T-cell ratio, requirement for cell contact and impact of soluble factors on the MSC-mediated effects. We also analyzed whether regulatory T cells could be modulated by MSC in co-cultures. METHODS: The effect of different MSC concentrations on T-cell proliferation induced by allogeneic, mitogenic or CD3/CD28 stimulation was analyzed using bromodeoxyuridine (BrdU) incorporation and carboxyfluorescein diacetate-succinimidyl ester (CFDA-SE) labeling. The level of regulatory T cells was assessed using quantitative real-time polymerase chain reaction (PCR) and flow cytometry analysis. RESULTS: MSC induced a dose- and contact-dependent inhibition of T-cell proliferation but lymphocytes from CB and PB were differentially affected. At low concentrations, MSC supported both CB and PB T-cell proliferation, rather than inhibiting their proliferation. This supportive effect was contact independent and soluble factors such interleukin-6 (IL-6) appeared to be involved. Interestingly, among the expanded T-cell population in both CB and PB, regulatory T cells were increased and were a part of the new cells promoted by MSC at low doses. CONCLUSIONS: MSC represent an attractive tool for reducing the lymphocyte response by inhibiting T-cell activation and proliferation as well as promoting tolerance by maintaining and promoting the expansion of regulatory cells. Nevertheless, the dual ability of MSC to either sustain or suppress T-cell proliferation according to conditions should be considered in the context of clinical applications.