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Minor Histocompatibility Antigens (minor + histocompatibility_antigen)
Selected AbstractsIdentification of therapeutically relevant mHags and strategies for mHag-based immunotherapy after allogeneic HSCT: where do we stand?ISBT SCIENCE SERIES: THE INTERNATIONAL JOURNAL OF INTRACELLULAR TRANSPORT, Issue n1 2010B. Eiz-Vesper Minor histocompatibility antigens (mHags) play a major role in graft-versus-host disease (GvHD) and graft-versus-leukaemia (GvL) effect following human leucocyte antigen (HLA)-matched hematopoietic stem cell transplantation (HSCT). These antigens are defined as immunogenic peptides derived from polymorphic proteins and can be recognized by allogeneic cytotoxic T cells (CTLs) in the context of HLA molecules. The tissue distribution of mHags and HLA molecules influences the clinical outcome of T-cell responses to these antigens. Differential T-cell recognition of mHags specifically expressed in hematopoietic cells, including malignant cells from the recipient, may result in a beneficial GvL effect without detrimental GvHD. Furthermore, T-cell responses against proteins solely expressed in hematopoietic cell lineages from which the malignancy is derived may be appropriate mediators of GvL reactivity without GvHD induction. mHags with hematopoiesis-restricted expression may therefore serve as primary targets of the T-cell-mediated GvL/graft-versus-tumour (GvT) effect following HLA-identical HSCT. This paper reviews the recent findings on methods for identification of mHags specifically functioning as GvL/GvT targets and outlines perspectives for the development of novel strategies for mHag-based immunotherapy. [source] Minor histocompatibility antigens as targets for immunotherapy using allogeneic immune reactionsCANCER SCIENCE, Issue 8 2007Yoshiki Akatsuka Minor histocompatibility antigens (mHag) were originally identified as antigens causing graft rejection or graft-versus-host disease in human leukocyte antigen (HLA)-matched allogeneic transplantation. Molecular identification has revealed most to be major histocompatibility complex (MHC)-bound short peptide fragments encoded by genes which are polymorphic due to single nucleotide polymorphisms (SNP). Genotypic disparity of SNP between transplantation donors and recipients gives rise to mHag as non-self antigens for both the donor and the recipient. Subsequently, mHag have been explored as immunotherapeutic antigens for use against recurring hematological malignancies after allogeneic hematopoietic cell transplantation (HCT), because mHag expressed only on hematopoietic cells are considered to augment graft-versus-leukemia/lymphoma (GVL) effects without increasing the risk of life-threatening graft-versus-host disease (GVHD). Accumulating evidence suggests that T-cell responses to mHag aberrantly expressed on solid tumor cells are also involved in the eradication of sensitive tumors such as renal cell carcinomas following HCT. Over the past decade, the number of putative GVL-directed mHag has increased to a level that covers more than 30% of the Japanese patient population, so that clinical trials may now be executed in the setting of either vaccination or adoptive immunotherapy. As it is expected that immune responses to alloantigens are more powerful than to tumor antigens mostly derived from overexpressed self-proteins, mHag-based immunotherapy may lead to a new treatment modality for high-risk malignancies following allogeneic HCT. (Cancer Sci 2007; 98: 1139,1146) [source] Decay Accelerating Factor is Essential for Successful Corneal EngraftmentAMERICAN JOURNAL OF TRANSPLANTATION, Issue 3 2010A. Esposito In contrast to immune restrictions that pertain for solid organ transplants, the tolerogenic milieu of the eye permits successful corneal transplantation without systemic immunosuppression, even across a fully MHC disparate barrier. Here we show that recipient and donor expression of decay accelerating factor (DAF or CD55), a cell surface C3/C5 convertase regulator recently shown to modulate T-cell responses, is essential to sustain successful corneal engraftment. Whereas wild-type (WT) corneas transplanted into multiple minor histocompatibility antigen (mH), or HY disparate WT recipients were accepted, DAF's absence on either the donor cornea or in the recipient bed induced rapid rejection. Donor or recipient DAF deficiency led to expansion of donor-reactive IFN-, producing CD4+ and CD8+ T cells, as well as inhibited antigen-induced IL-10 and TGF-,, together demonstrating that DAF deficiency precludes immune tolerance. In addition to demonstrating a requisite role for DAF in conferring ocular immune privilege, these results raise the possibility that augmenting DAF levels on donor corneal endothelium and/or the recipient bed could have therapeutic value for transplants that clinically are at high risk for rejection. [source] SiPep: a system for the prediction of tissue-specific minor histocompatibility antigensINTERNATIONAL JOURNAL OF IMMUNOGENETICS, Issue 4 2006M. Halling-Brown Summary Approximately 50 years ago it was found that inbred strains of mice were able to reject tumours and skin grafts from major histocompatibility complex (MHC) identical donors. They proposed that additional transplantation antigens must exist outside the MHC. These were described as minor histocompatibility antigens (mHAgs). Since then, related studies in humans have identified 16 human mHAgs. The aim of this work is to increase the number of known mHAgs by prediction of candidate minor histocompatibility loci by identifying coding single nucleotide polymorphisms (SNPs) where the amino acid variation lies within an MHC-binding peptide and alters the ability of that peptide to bind. We have developed an algorithm called SiPep which uses peptide sequences derived from the flanking regions of known non-synonymous SNPs, various MHC-binding and proteolytic cleavage evaluation methods and protein expression data to predict mHAgs. We have processed 45094 SNPs using the SiPep algorithm and have stored the results in a database called SNPBinder. The facilities to process submitted proteins through the SiPep algorithm as well as the SNPBinder database are available to the public. A set of peptides that are predicted as possible mHAgs by the SiPep algorithm have been tested using refolding assays and gel filtration and the results are presented in this paper. The SiPep tools and SNPBinder database are available free of charge via the internet. An HTML interface providing search facilities can be found at the following address: http://www.sipep.org/. [source] Sensitization to Minor Antigens Is a Significant Barrier in Bone Marrow Transplantation and Is Prevented by CD154:CD40 BlockadeAMERICAN JOURNAL OF TRANSPLANTATION, Issue 7 2010H. Xu Sensitization to major histocompatibility complex (MHC) alloantigens is critical in transplantation rejection. The mechanism of sensitization to minor histocompatibility antigens (Mi-HAg) has not been thoroughly explored. We used a mouse model of allosensitization to Mi-HAg to study the Mi-HAg sensitization barrier in bone marrow transplantation (BMT). AKR mice were sensitized with MHC congenic Mi-HAg disparate B10.BR skin grafts. Adaptive humoral (B-cells) and cellular (T cells) responses to Mi-HAg are elicited. In subsequent BMT, only 20% of sensitized mice engrafted, while 100% of unsensitized mice did. In vivo cytotoxicity assays showed that Mi-HAg sensitized AKR mice eliminated CFSE labeled donor splenocytes significantly more rapidly than naïve AKR mice but less rapidly than MHC-sensitized recipients. Sera from Mi-HAg sensitized mice also reacted with cells from other mouse strains, suggesting that Mi-HAg peptides were broadly shared between mouse strains. The production of anti-donor-Mi-HAg antibodies was totally prevented in mice treated with anti-CD154 during skin grafting, suggesting a critical role for the CD154:CD40 pathway in B-cell reactivity to Mi-HAg. Moreover, anti-CD154 treatment promoted BM engraftment to 100% in recipients previously sensitized to donor Mi-HAg. Taken together, Mi-HAg sensitization poses a significant barrier in BMT and can be overcome with CD154:CD40 costimulatory blockade. [source] | ||||||||||