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Expression profiling of rat MHC and NKC genes in skin explant assays reveals genes that are regulated in GVHD

ABSTRACT: Expression profiling of rat major histocompatibility complex and natural killer complex genes in skin explant assays reveals genes that are regulated in graft versus host disease. The major histocompatibility complex (MHC) is the most important genomic region that contributes to the genetic risk of graft rejection and graft versus host disease (GVHD) after haematopoietic stem cell transplantation. Therefore, MHC matching is most essential for the success of clinical transplantations. However, the MHC contains in addition to MHC class I and class II genes that are genotyped for selection of donors further so far unidentified genes that also contribute significantly to the risk to develop acute GVHD. It is difficult to identify these MHC genes by genetic association studies alone due to linkage disequilibrium in this region. Therefore, we aimed to identify MHC genes that might be involved in the pathohysiology of GVHD by expression profiling. To reduce the complexity of our model, we used genetically well-defined inbred rat strains (PVG and BN) and skin explant assays, an in-vitro-model of graft versus host reaction (GVHR), to analyse the expression of MHC and natural killer complex (NKC) genes in a cutaneous GVHR by a custom microarray. A higher percentage of genes in these immunologically highly important genomic regions were regulated than in the rest of the genome. We observed a statistically significant regulation of 25 MHC and 6 NKC genes and 168 other genes (i.e., 4.9%, 14.0%, and 6.6%, respectively) in rat skin explants cultured in the presence of pre-stimulated allogeneic lymphocytes compared to control samples cultured in the presence of syngeneic lymphocytes. Seven MHC and 3 NKC genes were selected for analysis by quantitative real-time polymerase chain reaction PCR. Most of the results of the microarray were confirmed in the same experimental set that was used for the microarray analysis and in a second independent experimental set of skin explant samples. In addition, GVHD-affected skin lesions of transplanted rats were analysed and similar regulations of most of the selected MHC and NKC genes were observed. Thus, our skin explant model of GVHR is informative for the gene regulation during GVHD. Interestingly, the human homologues of several of the regulated genes are polymorphic and could therefore contribute to the genetic risk of GVHD. These genes include RT1-Dmb, C2, Aif1, Spr1, Ubd, and Olr1. The human homologues of these genes might be useful for risk assessment and diagnosis of GVHD in patients. Two-condition experiment, Stimulated vs. NonSimulated cells. 12 Biological replicates, 2 Technical Replicates (Dye Swap) per Biological Replicate.

ORGANISM(S): Rattus norvegicus

SUBMITTER: Lennart Opitz

PROVIDER: E-GEOD-17928 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Expression profiling of rat major histocompatibility complex and natural killer complex genes in skin explant assays reveals genes that are regulated in graft versus host disease. The major histocompatibility complex (MHC) is the most important genomic region that contributes to the genetic risk of graft rejection and graft versus host disease (GVHD) after haematopoietic stem cell transplantation. Therefore, MHC matching is most essential for the success of clinical transplantations. However, the MHC contains in addition to MHC class I and class II genes that are genotyped for selection of donors further so far unidentified genes that also contribute significantly to the risk to develop acute GVHD. It is difficult to identify these MHC genes by genetic association studies alone due to linkage disequilibrium in this region. Therefore, we aimed to identify MHC genes that might be involved in the pathohysiology of GVHD by expression profiling. To reduce the complexity of our model, we used genetically well-defined inbred rat strains (PVG and BN) and skin explant assays, an in-vitro-model of graft versus host reaction (GVHR), to analyse the expression of MHC and natural killer complex (NKC) genes in a cutaneous GVHR by a custom microarray. A higher percentage of genes in these immunologically highly important genomic regions were regulated than in the rest of the genome. We observed a statistically significant regulation of 25 MHC and 6 NKC genes and 168 other genes (i.e., 4.9%, 14.0%, and 6.6%, respectively) in rat skin explants cultured in the presence of pre-stimulated allogeneic lymphocytes compared to control samples cultured in the presence of syngeneic lymphocytes. Seven MHC and 3 NKC genes were selected for analysis by quantitative real-time polymerase chain reaction PCR. Most of the results of the microarray were confirmed in the same experimental set that was used for the microarray analysis and in a second independent experimental set of skin explant samples. In addition, GVHD-affected skin lesions of transplanted rats were analysed and similar regulations of most of the selected MHC and NKC genes were observed. Thus, our skin explant model of GVHR is informative for the gene regulation during GVHD. Interestingly, the human homologues of several of the regulated genes are polymorphic and could therefore contribute to the genetic risk of GVHD. These genes include RT1-Dmb, C2, Aif1, Spr1, Ubd, and Olr1. The human homologues of these genes might be useful for risk assessment and diagnosis of GVHD in patients.

Project description:Regulatory T (Treg) cells play an important role in the induction and maintenance of peripheral tolerance. Treg cells also suppress a variety of other immune responses, including anti-tumor and alloimmune responses. We have previously reported that tumor-activated Treg cells express granzyme B and that granzyme B is important for Treg cell-mediated suppression of anti-tumor immune responses (GSE13409). Here, we report that allogeneic mismatch also induces the expression of granzyme B. Granzyme B-deficient mice challenged with fully mismatched allogeneic P815 mastocytoma cells have markedly improved survival compared to WT and other granzyme- or perforin-deficient mice, suggesting an immunoregulatory role for granzyme B in this setting. Treg cells harvested from the tumor environment of P815-challenged mice express granzyme B. Treg cells also express granzyme B in vitro during mixed lymphocyte reactions and in vivo in a mouse model of graft-versus-host disease (GVHD). However, in contrast to findings from our previously published tumor model, granzyme B is not required for the suppression of effector T cell (Teff) proliferation in in vitro Treg suppression assays stimulated by either Concanavalin A or allogeneic antigen presenting cells. Additionally, in an ex vivo assay, sort-purified in vivo-activated CD4+Foxp3+ Treg cells from mice with active GVHD -- under conditions known to induce granzyme B expression in Treg cells -- suppressed Teff cell proliferation in a granzyme B-independent manner. Adoptive transfer of naive granzyme B-deficient CD4+CD25+ Treg cells into a mouse model of GVHD rescued hosts from lethatlity equivalently to naive wild-type Treg cells. Serum analysis of GVHD-associated cytokine production in these recipients also demonstrated that Treg cells suppressed production of IL-2, IL-4, IL-5, GM-CSF, and IFN-gamma in a granzyme B-independent manner. In order to determine whether the context in which Treg cells are activated alters the intrinsic properties of Treg cells, we used Foxp3 reporter mice to obtain gene expression profiles of CD4+Foxp3+ Treg cells purifed from naive resting spleens, spleens from mice with acute GVHD, and from ascites fluid of mice challenged intraperitoneally with allogeneic P815 tumor cells. Unsupervised analyses revealed distinct activation signatures of Treg cells among the 3 experimental groups. Taken together, these findings demonstrate that granzyme B is not required for Treg cell-mediated suppression of GVHD, which is in contrast to what we have previously reported for Treg cell function in the setting of tumor challenge. Cell intrinsic differences could partially account for these differential phenotypes. These data also suggest the therapeutic potential of targeting specific Treg cell suppressive functions in order to segregate GVHD and graft-versus-tumor effector functions. Experiment Overall Design: Six replicates of Naive CD4+Foxp3+ Treg cells were purified from resting spleens, five replicates of allogeneic tumor-activated Treg cells and three samples of GVHD-activated Treg cells. Experiment Overall Design: Naive reps 1-3 are controls for the GVHD-activated samples. Experiment Overall Design: Naive reps 4-6 are controls for the Allogeneic tumor-activated samples.

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Expression profiling of rat MHC and NKC genes in skin explant assays reveals genes that are regulated in GVHD

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