Major Histocompatibility Antigens Research Articles

263. Characterization and Gene Transfer in Mesenchymal Stem Cells Derived from Human Umbilical Cord Blood

It has been shown that the stromal cell population found in bone marrow can be expanded and differentiated into cells with the phenotypes of bone, cartilage, muscle, neural and fat cells. However, whether or not mesenchymal stem cells (MSC) are present in human umbilical cord blood (UCB) has been the subject of ongoing debate. In this study, we report on a population of fibroblast-like cells derived from the mononuclear fraction of human UCB with osteogenic and adipogenic potential, and the presence of a subset of cells that have been maintained in continuous culture for more than six months. These cells were found to express CD29, CD44, CD90, CD95, CD105, CD166 and major histocompatibility antigen complex (MHC) class I, but not CD14, CD34, CD40, CD45, CD80, CD86, CD117, CD152 and MHC class II.

Epicutaneous immunization induces αβ T‐cell receptor CD4 CD8 double‐positive non‐specific suppressor T cells that inhibit contact sensitivity via transforming growth factor‐β

Since it was previously shown that protein antigens applied epicutaneously in mice induce allergic dermatitis mediated by production of T helper 2 (Th2) cytokines we postulated that this might induce suppression of Th1 immunity. Here we show that epicutaneous immunization of normal mice with a different protein antigen applied on the skin in the form of a patch induces a state of subsequent antigen-non-specific unresponsiveness caused by suppressor T cells (Ts) that inhibit sensitization and elicitation of effector T-cell responses. Suppression is transferable in vivo by alphabeta-T-cell receptor CD4(+) CD8(+) double positive lymphocytes harvested from lymphoid organs of skin patched animals and are not major histocompatibility complex-restricted nor antigen specific. Both CD25(+) and CD25(-) CD4(+) CD8(+) T cells are able to suppress adoptive transfer of Th1 effector cells mediating cutaneous contact sensitivity. In vivo treatment with monoclonal antibodies showed that the cytokines interleukin (IL)-4, IL-10 and transforming growth factor-beta (TGF-beta) are involved in the induction of the Ts cells. Additionally, using IL-10(-/-) mice we found that IL-10 is involved in skin induced tolerance. Further in vitro experiments showed that lymph node cells of skin tolerized mice non-specifically suppress [(3)H]thymidine incorporation by antigen-stimulated immune cells and this effect can be abolished by adding anti-TGF-beta, but not anti-IL-4 nor anti-IL-10 antibodies. These studies indicate the crucial role of TGF-beta in skin induced tolerance due to non-antigen-specific Ts cells and also show that IL-4, IL-10 and TGF-beta play an important role in the induction of epicutaneously induced Ts cell suppression.

Suppression extends to major histocompatibility antigens linked to tolerizing minor histocompatibility antigens, but not the other way round

'Active suppression', a mechanism of transplantation tolerance, can spread to newly introduced minor antigens once these antigens are linked to tolerizing antigens. We explored whether this suppression can extend to major histocompatibility (MHC) antigens and whether this phenomenon can be demonstrated once tolerance is induced to a MHC antigen. Mice were tolerized using donor bone marrow plus CD4 and CD8 monoclonal antibodies. The following strain combinations were used: AKR (H-2k) into CBA (H-2k), a multiple minor difference and B6 (H-2b) into B6(bm12) (H-2b), a MHC class II difference. Tolerance was tested by a donorskingraft. CBA mice tolerant to AKR received a second skin carrying either AKR antigens plus additional multiple minor antigens [F1(AKRxBalb.K)] or carrying additional minors and a MHC class I antigen (B10.AKM-H2M). B6(bm12) (H-2b) tolerant to B6 (H-2b) were grafted with skin from a Balb.B donor (Balb minors linked to the tolerizing class II antigen) or from a B10.A(3R) strain (a MHC class I antigen linked to the tolerizing class II antigen). CBA mice tolerant to AKR accepted F1(AKRxBalb.K) skin, whereas F1(CBAxBalb.K) were rejected. Rejection of B10.AKM/H2M skin by tolerant mice was delayed as compared with nontolerant mice. Tolerant and nontolerant B6(bm12) mice rejected Balb.B skin and B10.A(3R) skin within the same time. Thus, in this model, suppression was linked to minors. Alloreactivity against minors and majors could be suppressed. Suppression linked to a class II antigen could not be demonstrated.

Purification, crystallization and preliminary X-ray diffraction analysis of the human major histocompatibility antigen HLA-B*2703 complexed with a viral peptide and with a self-peptide

The product of the human leukocyte antigen (HLA) gene HLA-B*2703 differs from that of the prototypical subtype HLA-B*2705 by a single amino acid at heavy-chain residue 59 that is involved in anchoring the peptide N-terminus within the A pocket of the molecule. Two B*2703-peptide complexes were crystallized using the hanging-drop vapour-diffusion method using PEG 8000 as a precipitant. The crystals belong to space group P2(1) (pVIPR peptide) or P2(1)2(1)2(1) (pLMP2 peptide). Data sets were collected to 1.55 A (B*2703-pVIPR) or 2.0 A (B*2703-pLMP2) resolution using synchrotron radiation. With B*2705-pVIPR as a search model, a clear molecular-replacement solution was found for both B*2703 complexes.

Graft dysfunction and delayed immune reconstitution following haploidentical peripheral blood hematopoietic stem cell transplantation

For many children with life-threatening hematological diseases, hematopoietic stem cell transplantation (HSCT) is the only curative option. In children lacking a matched related or unrelated donor and with the certainty that, left untreated, death will ensue alternative donors must be sought. Haplo-identical peripheral blood stem cell transplantation (PBSCT) from a healthy parent is a feasible alternative. To reduce the risk of fatal graft-versus-host disease (GvHD) as a complication of transplant across major histocompatibility antigens, intense T-cell depletion is required. Large numbers of purified, cytokine mobilized peripheral stem cells (the so-called mega-dose concept) are required to compensate for the significantly increased risk of either graft failure or early rejection. In our unit, despite this approach, graft dysfunction has, in a significant group of children, proved problematic and, despite salvage attempts at re-transplantation, usually fatal. In children with hematological malignant disease, our overall relapse-free survival is 41%. However, successful transplant outcome has been associated with considerable delays in immune reconstitution that can be implicated in subsequent viral reactivation. We are investigating new strategies to improve the outcome of haplo-identical PBSCT, which may allow us to offer this form of treatment to more children requiring urgent HSCT.

Gastrointestinal complications of β2‐microglobulin amyloidosis: A case report and review of the literature

Introduction 2-microglobulin ( 2-M), the light chain of the class I major histocompatibility antigen, is a circulating protein that is impermeable to dialysis membranes. In the setting of renal failure, polymers of this protein accumulate and become amyloidogenic, possibly as a result of modification by advanced glycation end products. 2-M amyloidosis is a disabling complication of long-term hemodialysis or peritoneal dialysis with predominantly musculoskeletal manifestations. Patients present initially with shoulder pain, carpal tunnel syndrome, and flexor tenosynovitis of the hands. Less commonly, this type of amyloidosis may also present with visceral symptoms. Deposition of this amyloid protein in the blood vessels and interstitium of the gastrointestinal tract has been associated with abdominal pain, visceral perforation, pseudoobstruction, gastric and colonic dilatation, intestinal necrosis, malabsorption, and chronic diarrhea in patients on long-term hemodialysis. We report a patient with ischemic colitis related to 2-M amyloidosis and provide a summary of reported cases of gastrointestinal 2-M amyloidosis.

Immunopathogenesis of Acute Graft‐versus‐Host Disease: Implications for Novel Preventive and Therapeutic Strategies

AbstractFor Abstract see ChemInform Abstract in Full Text.

Pretransplant donor-specific transfusion accelerates complement-dependent cardiac allograft dysfunction

Sensitization to major histocompatibility antigens is no longer a contraindication to transplantation. New protocols prevent acute graft loss, but the residual effects of presensitization on graft survival are unknown. We have tested the role of early and late complement cascade in presensitized cardiac allograft recipients. C6-sufficient (C6 ) and -deficient (C6 ) female PVG.1U (RT1.A) rats underwent a blood transfusion from allogeneic PVG.R8 (RT1.A) rats or control isogeneic PVG.1U (RT1.A) rats. All blood recipients received cardiac allografts from PVG.R8 donors 3 weeks after transfusion. Low dose Cyclosporin A (5mg/kg on alternate days) was used for immunosupression after transplantation. Allogeneic but not control isologous blood transfusion elicited strong IgM and IgG alloantibody responses as measured with flow cytometry. A vigorous memory IgG response was elicited by cardiac allografts. Experimental C6 recipients rejected their transplants at an accelerated rate (4 days, n 5), compared with control C6 hosts (7 days, n 5). In contrast, allografts functioned until sacrifice at 90 days in 3 of 4 C6experimental recipients and all C6 control recipients (n 6). Presensitization by blood transfusion caused C6-deficient recipients to produce strong IgG antibodies until rejection or sacrifice. Circulating IgG alloantibodies were correlated with diffuse deposition of C4d on the vascular endothelium of the grafts in immunohistochemical stains. Transplant vasculopathy lesions characterized by smooth muscle proliferation and neointima formation were increased in the presensitized long-term C6-deficient group. In conclusion, presensitization by allogeneic blood transfusions caused accelerated graft rejection in the presence of the complete complement cascade. When the complement cascade is terminated at C6, presensitization resulted in increased deposition of split products of early complement components and more transplant vasculopathy.

An Update on the Functional Molecular Immunology (FIMM) Database

Data on the major histocompatibility complex, T-cell epitopes, B-cell epitopes, antigens and diseases are heterogeneous and scattered among different databases and the literature. Since it has become increasingly difficult to obtain an integrated view of functional immune response components, we have developed and updated over several years the Functional molecular IMMunology (FIMM) database (http:// research.i2r.a-star.edu.sg/fimm/). FIMM contains integrated expert-curated data on protein antigens, and on human immunological receptors that recognise and bind them in healthy or disease states. Interfaces with multiple, intuitive query options and query reports provide immunologists with prioritised information that aids data interpretation, vaccine target discovery and immune disease research.

MHC Disparity, Dose of Irradiation and T Cells in the Graft Determine the Persistence of Residual Host DCs, Mostly Skin-Derived Langerhans Cells (LCs) That Are Targets of DLI-Mediated Alloresponse.

Host antigen presenting cells (APCs), particularly DCs have a critical role in mediating allogeneic T-cell responses, however, the mechanisms that influence the donor DC reconstitution and persistence of residual host APCs after alloBMT are not characterized. We hypothesize that MHC disparity, pre-transplant conditioning and donor T cells directly influence donor DC reconstitution and amount of residual host DCs after alloBMT. To determine the role of major and minor histocompatibility antigens, syngeneic, B6Ly5.2 (H2b, CD45.1+) → C57BL/6 (H2b, CD45.2+), MHC-matched B6Ly5.2 (H2b, CD45.1+) → C3H.SW (H2b, CD45.2+) and MHC-mismatched C57BL/6 (H2b) → BALB/c (H2d) chimeras were constructed after lethal TBI (900 cGy) and transplantation of 1 x 107 bone marrow (BM) cells from corresponding donors. Six weeks later DC chimerism was determined in the spleen and subcutaneous axilary lymph nodes (LNs) based on the differential expression of CD45 marker. In all three sets of chimeras full reconstitution with donor-derived CD11c+ DCs was found in the spleen but significant amount of residual host DCs was found in the subcutaneous LNs of syngeneic (≈15%) and MHC-matched (≈10%) but not MHC-mismatched chimeras (<1%). Since the percentage of host DCs in the LNs of all three sets of chimeras varied despite receiving same amount of TBI and BM we concluded that the level of the residual host DCs elimination is directly influenced by the MHC disparity. To determine the role of conditioning we titrated the dose of TBI (200–900cGy) in the syngeneic model and measured donor DC chimerism 6 weeks after transplantation. Donor DC chimerism in the spleen increased proportionally to the TBI dose and reached 100% at 700 cGy dose. Increase in donor DC chimerism in subcutaneous LNs was slower and never exceeded 90%. Since there is no immunologic barrier in this donor → recipient pair we concluded that the level of donor DC chimerism is directly affected by the dose of TBI and that complete donor DC chimerism is never achieved in subcutaneous LNs. Next, we addressed the role of donor T cells. We focused on the MHC-matched alloBMT setting since the full donor chimerism in the spleen and subcutaneous LNs was readily achieved in the MHC-mismatched setting. B6Ly5.2 mice were conditioned with titrating dose of TBI (500–900) and received MHC-matched C3H.SW marrow with or without added 1 x 107 donor T cells. Presence of donor T cells in the graft clearly decreased the minimal dose of TBI required for engraftment of MHC-matched marrow from 700 to 500 cGy (p<0.001). However, once the MHC-matched marrow engrafted with or without added donor T cells there was a rapid conversion to full donor DC chimerism in the spleen but not in LNs. Increasing the dose of TBI from 900 to 1100 cGy did not significantly decrease the amount of residual host DCs in subcutaneous LNs. However, the amount of residual host DC chimerism in the LNs was clearly influenced by the presence of the donor T cells in the graft (900 cGy, 12.7% vs 4.4%). Next, by phenotypic analysis we characterized that dominant residual host DC populations in LNs are dermally-derived DCs and/or epidermally-derived LCs based on the high expression of DEC-205 marker. Finally, we tested whether residual host LCs are the target of DLI-mediated GVH-response. Administration of DLI resulted in decreased number of residual host LCs in the LNs (p< 0.01) providing the first evidence that residual host LCs are the targets of DLI-mediated GVH-response.

The Role of the bZip Protein Bach2 in Umbilical Cord Blood (UCB) T Lymphocytes.

Graft versus host disease (GVHD) occurring after allogeneic stem cell transplantation is mediated by donor T cell alloreactivity against major and minor histocompatibility antigens presented by recipient antigen presenting cells (APC). Clinical reports identify that umbilical cord blood (UCB) elicits reduced incidence and severity of GVHD due to reduced cytokine production. Nuclear factor of activated T cells (NFAT1) plays a pivotal role in the transcription of cytokine genes and other immune responses. NFAT1 regulates the expression of cytokine genes through direct interaction with AP-1 (Fos/Jun, basic-lucine zipper bZip proteins). NFAT1 and AP-1 cooperatively bind to a 15-bp DNA that contains both NFAT1 and AP-1 sites. We used Affymetrix oligonucleotide microarrays to compare gene expression of primary purified CD4+ UCB T-cells to adult peripheral blood CD4+ T-cells (AB) at baseline, 6, and 16 hours after primary stimulation with anti-CD3/anti-CD28. NFAT-regulated genes exhibited lower expression in UCB CD4+ T-cells including: GM-CSF, IFN- g, TNF-a, IL-3, IL-4, IL-5, IL-13, IL- 2R (CD 25). In addition, AP-1 (Fos/Jun) did not show a significant change. However, Bach2, an 841- amino-acid-residue containing bZip protein, did show a significant increase in UCB CD4+ T-cells. Previous reports identify from the crystal structure of the quaternary complex of NFAT1/AP-1/DNA (Chen et al., Nature 1998) that NFAT1 is in contact with the lucine zipper region of AP-1 while the basic region of AP-1 binds to the DNA site at TGTTTCA. The amino-acid residues that make contact with DNA in the bZip regions of Jun and Fos are highly conserved in the Jun and Fos families. These amino acid residues are also 100% conserved in the human and mouse Bach2. The high similarity of DNA-contacting amino-acid residues between Bach2 and AP-1 strongly suggests that Bach2 and AP-1 may bind to the same DNA site. We hypothesize that Bach2 may act as a transcriptional repressor of cytokine genes due to the fact that increased Bach2 in UCB may compete with AP-1 for same DNA binding site, which in turn may partly block the interaction of NFAT1 with AP-1 and the expression of cytokine genes in UCB. We are currently pursuing this hypothesis. Ongoing studies are to confirm whether the protein levels of Bach2 and AP-1 are different in UCB compared to with AB CD4+ T-cells. This includes using gel-shift assays in vitro to test Bach2 binding to the DNA site of AP-1 as well as to test potential competitive binding of Bach2 and AP-1 to the same DNA site.

Novel approaches to the therapy of steroid-resistant acute graft-versus-host disease

Novel approaches to the therapy of steroid-resistant acute graft-versus-host disease

Inhibition of alloresponse by a human trophoblast non-coding RNA suppressing class II transactivator promoter III and major histocompatibility class II expression in murine B-lymphocytes

Trophoblasts are a model of natural allograft tolerance. A unique characteristic is the complete lack of expression of all classic major histocompatibility (MHC) antigens. We cloned a human trophoblast non-coding RNA (TncRNA) that suppresses MHC class II expression through inhibition of the class II transactivator (CIITA) promoter. We assessed the functional affects of TncRNA on an alloresponse and dissected the functional domain on CIITA promoter III. Murine B-cell line A20 was transfected with TncRNA. Class II suppressed clones were selected and characterized by flow cytometry and Northern analysis. The clones were then subjected to lymphocyte proliferation assay to assess the stimulation of T-lymphocytes. CIITA promoter III-luciferase reporter plasmids were used with TncRNA plasmids in co-transfection assays; 5'-end deletion plasmids were used to dissect the promoter. Significant suppression of I-Ad expression was seen. Northern blot scans demonstrated 84% to 93% suppression of class II transcripts. Lymphocyte proliferation assay demonstrated a 50% and 64% inhibition of lymphocyte stimulation in the 2 clones, compared to A20 wild type. Dissection of promoter III indicated that an area between bp -152 to -107 contains the functional site of TncRNA. Human TncRNA is active across species lines and significantly inhibits allogenic response to B-cells. There is concurrent suppression of constitutive class II expression in TncRNA clones mediated through a defined region of CIITA promoter III.

Update on graft versus host disease.

Update on graft versus host disease.

Complex assembly, crystallization and preliminary X-ray crystallographic studies of MHC H-2Kd complexed with an HBV-core nonapeptide.

In order to establish a system for structural studies of the murine class I major histocompatibility antigen complex (MHC) H-2Kd, a bacterial expression system and in vitro refolding preparation of the complex of H-2Kd with human beta2m and the immunodominant peptide SYVNTNMGL from hepatitis B virus (HBV) core-protein residues 87-95 was employed. The complex (45 kDa) was crystallized; the crystals belong to space group P222(1), with unit-cell parameters a = 89.082, b = 110.398, c = 47.015 A, alpha = beta = gamma = 90 degrees. The crystals contain one complex per asymmetric unit and diffract X-rays to at least 2.06 A resolution. The structure has been solved by molecular replacement and is the first crystal structure of a peptide-H-2Kd complex.

MHC class I manipulation on cell surfaces by gene transfer of anti-MHC class I intrabodies—a tool for decreased immunogenicity of allogeneic tissue and cell transplants

Intrabodies (IB) are suitable tools to down-regulate the expression of cell surface molecules in general. In this work, the appearance of major histocompatibility (MHC) class I molecules on the cell surface could be prevented by the expression of intracellularly localized anti-MHC class I antibodies. The expression of MHC antigens presenting intracellularly synthetised peptides on the cell surface is the predominant reason for immunologic detection and rejection of allogeneic cell and tissue transplants. Allogeneic keratinocyte sheets might be a suitable tool for skin grafting. Within this study primary rat keratinocytes have been transfected with anti-MHC I-IB. Strong IB-expressing cells showed a MHC I “knockout” phenotype. The cells did not exhibit any significant alterations compared to non-transfected cells: the cell growth and the expression of other surface molecules were unaltered. Merely an enhanced intracellular accumulation of MHC I molecules could be detected. Notably, IB-expressing keratinocytes displayed a reduced susceptibility to allogeneic cytotoxic T cells in vitro compared to unmodified cells with a normal level of MHC I surface expression. These MHC I-deficient keratinocytes might be utilized in tissue-engineered allogeneic non-immunogeneic skin transplants. The principle of MHC class I manipulation in general can be used for other allogeneic cell and tissue-engineered transplants as well.

CO-STIMULATORY INHIBITION THROUGH CD134 (OX40) BLOCKADE PROMOTES MURINE HEART ALLOGRAFT SURVIVAL

P1031 Aims: CD134 is a co-stimulatory molecule that is expressed as a late event in T cell activation and contributes to the generation of immunological memory. CD134 blockade effectively ameliorates inflammation in models of autoimmune disease but its role in transplantation has hitherto been little studied. Methods: An OX40-Ig fusion protein was used to investigate the role of this co-stimulatory molecule in alloimmunity both in vitro, through addition of the fusion protein to allogeneic lymphocyte co-cultures, and in vivo through administration of OX40-Ig to mouse recipients of vascularised heart allografts. The role of CD134 was studied in mouse strain combinations representing both major histocompatibility (MHC, BALB/c to CBA/Ca) and minor histocompatibility (mHC, B10.BR to CBA/Ca) antigen mismatched tissues. Results: In vitro T cell activation following encounter with alloantigen resulted in delayed expression of CD134, as has been reported previously for T cells activated by nominal protein antigens. Alloantigen-stimulated T cells expressed increasing levels of CD25 and CD69 until 72 hours post stimulation, but similar levels of CD134 expression were not seen until 96 hours. Addition of OX40-Ig to lymphocyte co-cultures inhibited proliferation in a dose-dependent manner by up to 83% in both MHC and mHC mismatched strain combinations. Interestingly, CD134 blockade was most effective when addition of the OX40-Ig fusion protein was delayed until day 4 of co-culture, corresponding to maximum CD134 expression on activated responder cells. MHC mismatch-induced proliferation was inhibited by 84% when addition was delayed for 96 hours, compared with 0% inhibition when OX40-Ig was added at 24 hours. In the minor mismatch strain combination, inhibition of proliferation was 86% at 96 hours compared with 42% at 24 hours. Similarly, cytokine production (IFN-γ, IL-2 and IL-10) in lymphocyte co-cultures was markedly inhibited in a time-dependent manner following addition of OX40-Ig. When administered in vivo, daily for 15 days, OX40-Ig failed to extend graft survival in the major mismatch strain combination (median survival time [MST] 8 days in both treated and non-treated groups). In contrast, OX40-Ig was highly effective at prolonging the survival of B10.BR heart allografts in CBA/Ca recipients (mHC mismatch, MST extended from 14 [n=7] to >100 days [n=11]). Immunohistological analysis of the transplanted hearts revealed that both rejecting and long-surviving heart grafts had similar degrees of mononuclear cell infiltration but that OX40-Ig treatment appears to delay the cellular infiltration. Conclusions: We conclude that CD134/CD134L interaction plays an important role in the co-stimulatory cascade and that blockade of this molecular interaction may be of therapeutic value in helping to prevent allograft rejection.

Major histocompatibility antigen expression on the bovine placenta: its relationship to abnormal pregnancies and retained placenta

In viviparous animals, regulation of expression of major histocompatibility complex (MHC) class I antigens by the trophoblast cells, which constitute the outermost layer of the placenta, seems to be critical for maternal immunological acceptance of an allogeneic fetus. Cattle are unusual in this regard, since the bovine trophoblast cells, in specific regions of the uterine/placental interface, normally express MHC class I antigens during the third trimester of gestation. This expression appears to be biologically relevant as MHC class I compatibility between a cow and her fetus has been associated with an increased incidence of placental retention. We have found significant differences in lymphocyte populations, cytokine production, and trophoblast cell apoptosis in the placentomes of MHC-compatible and -incompatible pregnancies at parturition. This suggests that maternal immunological recognition of fetal MHC class I proteins triggers an immune/inflammatory response that contributes to placental separation at parturition in cattle. Early in pregnancy, a complete shutdown of MHC class I expression by trophoblast cells appears to be critical for normal placental development and fetal survival. In bovine somatic cell nuclear transfer (SCNT) pregnancies, there is an extremely high rate of fetal loss between days 30 and 90 of pregnancy. We have shown that in bovine SCNT pregnancies, between days 34 and 63 of gestation, there is both abnormal expression of MHC class I antigens by trophoblast cells and an abnormal accumulation of lymphocytes within the uterine stroma. Consequently, it is likely that activation of the maternal mucosal immune system, within the uterus at the same time when placentomes are being established, interferes with the process of placentome development and leads to immune-mediated abortion. Our data suggest that bovine MHC-compatible pregnancies provide a unique model for studying regulation of the uterine immune system, as well as immune-mediated placental rejection.

Application of discordant sib-pair linkage analysis for mapping minor histocompatibility antigen loci in a novel graft-vs-host-disease model.

Graft-vs-host disease (GVHD) is an adverse effect of allogenic bone marrow transplantation. Although a major cause of GVHD following bone marrow transplantation is incompatibility of major histocompatibility antigen (human leukocyte antigen, HLA) in donor-recipient pairs, the incompatibility of minor histocompatibility antigen (mHa) is known as another cause, especially in HLA-matched donor-recipient pairs. In 1998, Lunetta and Rogus proposed the use of discordant sib-pair (DSP) linkage analysis for detecting mHa and calculated the statistical power using the GVHD model, assuming single mHa locus with multiple alleles. Recently, we proposed a different GVHD model, assuming multiple mHa loci with two alleles (biallelic), considering the single-nucleotide polymorphisms. When the effect of each mHa locus on the occurrence of GVHD is independent, the possible triangle for DSP proposed by Lunetta and Rogus is not optimum, but a new possible triangle, named here as GVHD region, is needed. We evaluated, based on Monte Carlo simulation, the test criteria [log of odds (lod) score cutoffs] and power of DSP using the GVHD region for various parameter sets. The GVHD region showed a higher power than the DSP and entire regions in plausible situations. Our results suggest that the application of GVHD region to DSP is effective for the screening of mHa loci.

Immunopathogenesis of acute graft-versus-host disease: implications for novel preventive and therapeutic strategies.

Acute graft-versus-host disease (GVHD) is a primary T-cell-mediated complication of allogeneic hematopoietic stem cell transplantation (HSCT), occurring when donor-derived T cells are stimulated by host antigen-presenting cells (APCs), enhanced by proinflammatory cytokines such as interleukin (IL)-1, IL-6, IL-8, and tumor necrosis factor (TNF)-alpha. Recent data indicate that besides differences in major histocompatibility and minor histocompatibility antigens, cytokine gene polymorphisms have a predictive value for the complication of GVHD. Patients with a high anti-inflammatory IL-10 production have been demonstrated to be protected from GVHD while patients with high TNF-alpha serum levels were more at risk for GVHD. Pharmacological immunosuppression for GVHD prophylaxis and therapy, including unspecific approaches with corticosteroids or methotrexate (MTX), as well as more specific therapy with cyclosporin A (CsA), tacrolimus (FK506), sirolimus, mycophenolate mofetil (MMF), antithymocyte globulin (ATG), and monoclonal antibodies (MAbs) directed against CD3, CD25, CD52, cytotoxic T-lymphocyte antigen (CTLA)-4, CD40 ligand, or TNF-alpha, have been proven to be effective. Recent data on novel techniques to selectively deplete alloreactive T cells by removal, destruction, or anergy induction while preserving leukemia-specific T-cell clones suggest a clinical benefit from these approaches. Gene-modified T cells that can selectively be depleted and CD4(+)CD25(+) regulatory T cells are under investigation for their ability to modulate alloreactivity after HSCT. With a better understanding of the immunopathogenesis of acute GVHD and the technical improvement of recently described therapeutic approaches, such as removal of naive T cells, selection of Th2 cells, suicide gene transduced T cells, and adoptive transfer of regulatory T cells, the use of alloreactivity as a treatment modality may be expanded to nonhematological disease entities such as solid tumors or autoimmune disorders.