Non-classical Major Histocompatibility Complex Research Articles

CREB1 promotes expression of immune checkpoint HLA-E leading to immune escape in multiple myeloma

Multiple myeloma (MM) cells effectively escape anti-tumoral immunity to survive in the tumor microenvironment (TME). Herein, we identify non-classical major histocompatibility complex (MHC) class I molecule HLA-E as a major contributing factor in immune escape. Clinically, HLA-E expression correlates with aggressive disease features such as t(4;14) and CD56 expression and is induced by IFN-gamma (IFN-γ) in the TME. We discovered that HLA-E is regulated by cAMP responsive element binding protein 1 (CREB1) transcription factor by direct promoter binding; genomic and pharmacological inhibition of CREB1 reduced HLA-E levels even in the presence of IFN-γ or IFN-γ activating agents, such as immunomodulatory drugs and panobinostat. HLA-E binds to natural killer group 2A (NKG2A), delivering an inhibitor signal to natural killer (NK) cells. Treatment with a CREB1 inhibitor was able to restore NK cell-mediated cytotoxicity against MM cell lines and patient samples. In conclusion, our results strongly demonstrate that CREB1 inhibition promotes anti-tumoral immunity in MM by limiting HLA-E expression and enhancing the activity of NK cells.

How the Soluble Human Leukocyte Antigen-G levels in Amniotic Fluid and Maternal Serum Correlate with the Feto-Placental Growth in Uncomplicated Pregnancies.

Introduction: Trophoblast-derived angiogenic factors are considered to play an important role in the pathophysiology of various complications of pregnancy. Human Leukocyte Antigen-G (HLA-G) belongs to the non-classical human major histocompatibility complex (MHC-I) molecule and has membrane-bound and soluble forms. HLA-G is primarily expressed by extravillous cytotrophoblasts located in the placenta between the maternal and fetal compartments and plays a pivotal role in providing immune tolerance. The aim of this study was to establish a relationship between concentrations of soluble HLA-G (sHLA-G) in maternal serum and amniotic fluid at 16-22 weeks of gestation and the sonographic measurements of fetal and placental growth. Materials and methods: sHLA-G in serum and amniotic fluid, as well as fetal biometric data and placental volume and perfusion indices, were determined in 41 singleton pregnancies with no complications. The level of sHLA-G (U/mL) was tested with a sandwich enzyme-linked immunosorbent assay (ELISA) kit. Results: The sHLA-G levels were unchanged both in amniotic fluid and serum during mid-pregnancy. The sHLA-G level in serum correlated positively with amniotic sHLA-G level (β = 0.63, p < 0.01). Serum sHLA-G level was significantly correlated with abdominal measurements (β = 0.41, p < 0.05) and estimated fetal weight (β = 0.41, p < 0.05). Conversely, amniotic sHLA-G level and placental perfusion (VI: β = -0.34, p < 0.01 and VFI: β = -0.44, p < 0.01, respectively) were negatively correlated. A low amniotic sHLA-G level was significantly associated with nuchal translucency (r = -0.102, p < 0.05). Conclusions: sHLA-G assayed in amniotic fluid might be a potential indicator of placental function, whereas the sHLA-G level in serum can be a prognostic factor for feto-placental insufficiency.

In silico identification and characterization of small molecule binding to the CD1d immunoreceptor

CD1 immunoreceptors are a non-classical major histocompatibility complex (MHC) that present antigens to T cells to elucidate immune responses against disease. The antigen repertoire of CD1 has been composed primarily of lipids until recently when CD1d-restricted T cells were shown to be activated by non-lipidic small molecules, such as phenyl pentamethyl dihydrobenzofuran sulfonate (PPBF) and related benzofuran sulfonates. To date structural insights into PPBF/CD1d interactions are lacking, so it is unknown whether small molecule and lipid antigens are presented and recognized through similar mechanisms. Furthermore, it is unknown whether CD1d can bind to and present a broader range of small molecule metabolites to T cells, acting out functions analogous to the MHC class I related protein MR1. Here, we perform in silico docking and molecular dynamics simulations to structurally characterize small molecule interactions with CD1d. PPBF was supported to be presented to T cell receptors through the CD1d F’ pocket. Virtual screening of CD1d against more than 17,000 small molecules with diverse geometry and chemistry identified several novel scaffolds, including phytosterols, cholesterols, triterpenes, and carbazole alkaloids, that serve as candidate CD1d antigens. Protein-ligand interaction profiling revealed conserved residues in the CD1d F’ pocket that similarly anchor small molecules and lipids. Our results suggest that CD1d could have the intrinsic ability to bind and present a broad range of small molecule metabolites to T cells to carry out its function beyond lipid antigen presentation. Communicated by Ramaswamy H. Sarma

Intrinsic factors and CD1d1 but not CD1d2 expression levels control invariant natural killer T cell subset differentiation

Invariant natural killer T (NKT) cell subsets are defined based on their cytokine-production profiles and transcription factors. Their distribution is different in C57BL/6 (B6) and BALB/c mice, with a bias for NKT1 and NKT2/NKT17 subsets, respectively. Here, we show that the non-classical class I-like major histocompatibility complex CD1 molecules CD1d2, expressed in BALB/c and not in B6 mice, could not account for this difference. We find however that NKT cell subset distribution is intrinsic to bone marrow derived NKT cells, regardless of syngeneic CD1d-ligand recognition, and that multiple intrinsic factors are likely involved. Finally, we find that CD1d expression levels in combination with T cell antigen receptor signal strength could also influence NKT cell distribution and function. Overall, this study indicates that CD1d-mediated TCR signals and other intrinsic signals integrate to influence strain-specific NKT cell differentiation programs and subset distributions.

An Ancestral Major Histocompatibility Complex Organization in Cartilaginous Fish: Reconstructing MHC Origin and Evolution.

Cartilaginous fish (sharks, rays, and chimeras) comprise the oldest living jawed vertebrates with a mammalian-like adaptive immune system based on immunoglobulins (Ig), T-cell receptors (TCRs), and the major histocompatibility complex (MHC). Here, we show that the cartilaginous fish "adaptive MHC" is highly regimented and compact, containing (i) a classical MHC class Ia (MHC-Ia) region containing antigen processing (antigen peptide transporters and immunoproteasome) and presenting (MHC-Ia) genes, (ii) an MHC class II (MHC-II) region (with alpha and beta genes) with linkage to beta-2-microglobulin (β2m) and bromodomain-containing 2, (iii) nonclassical MHC class Ib (MHC-Ib) regions with 450 million-year-old lineages, and (iv) a complement C4 associated with the MHC-Ia region. No MHC-Ib genes were found outside of the elasmobranch MHC. Our data suggest that both MHC-I and MHC-II genes arose after the second round of whole-genome duplication (2R) on a human chromosome (huchr) 6 precursor. Further analysis of MHC paralogous regions across early branching taxa from all jawed vertebrate lineages revealed that Ig/TCR genes likely arose on a precursor of the huchr9/12/14 MHC paralog. The β2m gene is linked to the Ig/TCR genes in some vertebrates suggesting that it was present at 1R, perhaps as the donor of C1 domain to the primordial MHC gene. In sum, extant cartilaginous fish exhibit a conserved and prototypical MHC genomic organization with features found in various vertebrates, reflecting the ancestral arrangement for the jawed vertebrates.

CREB1 Promotes Immune Escape of Multiple Myeloma Cells By Inducing HLA-E

Introduction: Multiple Myeloma (MM) is a disease of clonal plasma cells, which accumulate in the bone marrow (BM) and rely on the support of the microenvironment to survive. Immune escape is a common resistance mechanism employed by tumor cells to avoid cytotoxicity by effector immune cells. HLA-E, a non-classical major histocompatibility complex (MHC) class I molecule, inhibits the function of specific subtypes of Natural Killer (NK) and T cells, leading to tumor immune escape. HLA-E expression correlates with worse progression-free survival in newly diagnosed patients with MM. Therefore, we decided to better elucidate the function and regulation of HLA-E expression in MM. Results: We observed that HLA-E mRNA expression increases in the transformation from normal plasma cells to MM. Since INF-gamma induces HLA-E in MM cells and CREB1 itself promotes the production of IFN-gamma, we hypothesize that CREB1 could regulate HLA-E expression in MM. We first analyzed RNA-sequencing data from patients with MM in the CoMMpass database: gene set enrichment analysis (GSEA) showed increased expression of several pathways related to interferon signaling in patients with high CREB1 expression. We then specifically looked at differences in HLA-E and we confirmed that patients with high CREB1 expression had statistically significant higher HLA-E levels compared with patients with low CREB1 expression. CHIP-sequencing assays in MM cell lines demonstrated that CREB1 can directly influence HLA-E expression by binding to HLA-E promoter. To further prove these data, we evaluated HLA-E levels in gain-of and loss-of function models of CREB1. We observed an increase of HLA-E levels by overexpression of wild type CREB1 and reduction of HLA-E levels by CREB1 silencing or pharmacological inhibition of CREB1 with 666-15 (CREBi). We then investigated the relationship between CREB1 and STAT1. Indeed, IFN-gamma signals through the STAT1-JAK pathway. Interestingly, while treatment with IFN-gamma strongly induces HLA-E without affecting CREB1 levels or its function, CREBi + INF-gamma reduces HLA-E, STAT1, and phospho-STAT1 levels. Conversely, immunomodulatory drugs (lenalidomide-LEN and pomalidomide-POM) and HDAC inhibitor, Panobinostat, promote the phosphorylation of STAT1, resulting in the transcription of IFN-target genes, including HLA-E. The increase in HLA-E was then reverted by CREB1 inhibition. Since HLA-E impairs NK cell function, we treated MM cells in the presence of NK cells with CREBi alone or in combination with immunomodulatory drugs (IMiDs). Treatment with CREBi or CREBi + IMiDs potentiated the killing effects of NK cells. Animal studies are ongoing to confirm these data in vivo. Conclusion: In conclusion, our study defines the role of CREB1 in modulating HLA-E expression; CREB1 inhibition improves NK cell-mediated cytotoxicity in MM, representing a novel strategy to tackle immune escape.

Investigation the role of Human Leukocyte Antigen-G in Iraqi patients with papillary thyroid carcinoma

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility complex (MHC) protein with well-known immunomodulatory characteristics. It is also believed to be an important sign of immune tolerance in cancer cells. Immune Escape. HLA-G is also associated with disease development and prognosis in cancer patients. The goal of this study was to compare soluble HLA-G (sHLA-G) levels before and after radioactive iodine therapy (RAI) by enzyme immunoassay (ELISA). Immunohistochemistry was used to examine HLA-G protein expression in thyroid tissues from patients with papillary thyroid cancer (PTC) to investigate the relationship between HLA-G expression and patients' clinical variables. Prospective research included 138 blood samples from patients and controls, as well as 25 thyroid paraffin-embedded tissues from individuals suffering from papillary thyroid cancer (PTC) and controls. Our findings demonstrated a significant difference in the means of people who had radioactive iodine therapy against those who did not (Mean SE = 4.19 0.31, 2.216 0.08, respectively). HLA-G staining, on the other hand, was identified in tumor cells in papillary thyroid cancer, all sections were positive, strongly stained and completely membranous, indicating the presence of HLA-G protein in the tested material. These findings suggest that HLA-G may be involved in the pathogenesis of papillary thyroid cancer.

Association between major histocompatibility complex haplotypes and susceptibility of unvaccinated and vaccinated cattle to paratuberculosis

Bovine Johne’s disease (BJD) or paratuberculosis is caused by Mycobacterium avium spp. paratuberculosis (MAP) and is a worldwide problem among domestic and wild ruminants. While vaccines are available, natural differences in background immunity between breeds within species and between individuals within herds suggest that genetic differences may be able to be exploited in marker-assisted selection as an aid to disease control. The major histocompatibility complex (MHC) is an important component in immune recognition with considerable genetic variability. In this study, associations between the MHC and resistance to BJD were explored in dairy cattle across two herds in which some of the cattle had been vaccinated with Silirum® (n = 540 cows). A BJD susceptible animal was exposed to MAP and became infected, while a resistant animal was exposed but did not become infected. There are different ways to define both exposure and infection, with different levels of stringency, therefore many classifications of the same set of animals are possible and were included in the analysis. The polymorphic regions of major histocompatibility complex class I (MHC I) and class II (MHC II) genes were amplified from the genomic DNA by PCR and sequenced, targeting exons 2 and 3 of the classical and non-classical MHC I genes and exon 2 from the DRB3, DQA1, DQA2 + 3 and DQB MHC II genes. The frequencies of MHC I and MHC II haplotypes and alleles were determined in susceptible and resistant populations. In unvaccinated animals, seven MHC I haplotypes and seven MHC II haplotypes were associated with susceptibility while two MHC I and six MHC II haplotypes were associated with resistance (P < 0.05). In vaccinated animals, two MHC I and three MHC II haplotypes were associated with susceptibility, while one MHC I and two MHC II haplotypes were associated with resistance (P < 0.05). The alleles in significant haplotypes were also identified. Case definitions with higher stringency resulted in fewer animals being included in the analyses, but the power to detect an association was not reduced and there was an increase in strength and consistency of associations. Consistent use of stringent case definitions is likely to improve agreement in future association studies.

The non-classical major histocompatibility complex II protein SLA-DM is crucial for African swine fever virus replication

African swine fever virus (ASFV) is a lethal animal pathogen that enters its host cells through endocytosis. So far, host factors specifically required for ASFV replication have been barely identified. In this study a genome-wide CRISPR/Cas9 knockout screen in porcine cells indicated that the genes RFXANK, RFXAP, SLA-DMA, SLA-DMB, and CIITA are important for productive ASFV infection. The proteins encoded by these genes belong to the major histocompatibility complex II (MHC II), or swine leucocyte antigen complex II (SLA II). RFXAP and CIITA are MHC II-specific transcription factors, whereas SLA-DMA/B are subunits of the non-classical MHC II molecule SLA-DM. Targeted knockout of either of these genes led to severe replication defects of different ASFV isolates, reflected by substantially reduced plating efficiency, cell-to-cell spread, progeny virus titers and viral DNA replication. Transgene-based reconstitution of SLA-DMA/B fully restored the replication capacity demonstrating that SLA-DM, which resides in late endosomes, plays a crucial role during early steps of ASFV infection.

The Molecular Mechanisms of HLA-G Regulatory Function on Immune Cells during Early Pregnancy.

Human leukocyte antigen-G (HLA-G) is a non-classical human major histocompatibility complex (MHC-I) molecule with the membrane-bound and soluble types. HLA-G is primarily expressed by extravillous cytotrophoblast cells located at the maternal-fetal interface during pregnancy and is essential in establishing immune tolerance. This review provides a comprehensive understanding of the multiple molecular mechanisms by which HLA-G regulates the immune function of NK cells. It highlights that HLA-G binds to microRNA to suppress NK cell cytotoxicity and stimulate the secretion of growth factors to support fetal growth. The interactions between HLA-G and NK cells also activate senescence signaling, promoting spiral artery remodeling and maintaining the balance of maternal-fetal immune responses. In addition, HLA-G can inhibit the function of decidual T cells, dendritic cells, and macrophages. Overall, the interaction between trophoblast cells and immune cells mediated by HLA-G plays a crucial role in understanding immune regulation at the maternal-fetal interface and offers insights into potential treatments for pregnancy-related diseases.

Human leukocyte antigen-G in gynaecological tumours.

Gynaecological tumours that threaten the health of women, especially when advanced and recurrent, have remained mostly intractable to existing treatments. Therefore, new therapeutic targets are urgently needed. Human leukocyte antigen-G (HLA-G) is a nonclassical major histocompatibility complex class I molecule typically expressed in foetuses for protection against destruction by the maternal immune system. HLA-G is also expressed under pathological conditions, such as in solid tumours, and may participate in tumour development and serve as a novel immune checkpoint in cancer. Furthermore, it is expressed in most gynaecological tumours. Therefore, inhibiting HLA-G and its receptors to block the immune escape pathway could represent a new strategy in cancer immunotherapy. To the best of our knowledge, this review is the first to summarize recent research findings on HLA-G in gynaecological oncology. We highlight the fact that HLA-G is expressed in gynaecological tumour tissues, wherein it inactivates immune effectors involved in tumour progression. Further studies on HLA-G in gynaecological oncology are needed to incorporate HLA-G into the design and evaluation of immunotherapy for malignant gynaecological diseases.

Prognostic value of human leukocyte antigen G (HLA-G) expression in solid tumors: A systematic review and meta-analysis.

e14639 Background: Identification of modulators of the immune response with inhibitory properties that could be susceptible for therapeutic intervention is a key goal in cancer research. An example is the human leukocyte antigen G (HLA-G), a nonclassical major histocompatibility complex (MHC) class I molecule, involved in cancer progression. Methods: We performed a systematic review and meta-analysis on the role of HLA-G expression and outcome in solid tumors. A total of 25 studies met the inclusion criteria comprising data from 4871 patients reporting overall survival (OS) outcomes, and 961 patients, in 5 studies, for disease free survival (DFS). This study was performed in accordance with PRISMA guidelines and registered in PROSPERO. Results: HLA-G expression was associated with worse OS (HR 2.09, 95% CI = 1.67 to 2.63; P &lt; .001), that was higher in gastric (HR = 3.40; 95% CI = 1.64 to 7.03), pancreatic (HR = 1.72; 95% CI = 0.79 to 3.74) and colorectal (HR = 1.55; 95% CI = 1.16 to 2.07) cancer. No significant differences were observed between the most commonly utilized antibody (4H84) and other methods of detection. HLA-G expression was associated with DFS which approached but did not meet statistical significance. Conclusions: We describe the first meta-analysis associating HLA-G expression and worse survival in a variety of solid tumors.

Prognostic value of human leukocyte antigen G expression in solid tumors: a systematic review and meta-analysis.

Identification of modulators of the immune response with inhibitory properties that could be susceptible for therapeutic intervention is a key goal in cancer research. An example is the human leukocyte antigen G (HLA-G), a nonclassical major histocompatibility complex (MHC) class I molecule, involved in cancer progression. In this article we performed a systematic review and meta-analysis on the association between HLA-G expression and outcome in solid tumors. This study was performed in accordance with PRISMA guidelines and registered in PROSPERO. A total of 25 studies met the inclusion criteria. These studies comprised data from 4871 patients reporting overall survival (OS), and 961 patients, reporting disease free survival (DFS). HLA-G expression was associated with worse OS (HR 2.09, 95% CI = 1.67 to 2.63; P < .001), that was higher in gastric (HR = 3.40; 95% CI = 1.64 to 7.03), pancreatic (HR = 1.72; 95% CI = 0.79 to 3.74) and colorectal (HR = 1.55; 95% CI = 1.16 to 2.07) cancer. No significant differences were observed between the most commonly utilized antibody (4H84) and other methods of detection. HLA-G expression was associated with DFS which approached but did not meet statistical significance. In summary, we describe the first meta-analysis associating HLA-G expression and worse survival in a variety of solid tumors. https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022311973.

Chemical Synthesis and Molecular Interaction Analysis of α-Galactosyl Ceramide Derivatives as CD1d Ligands.

CD1d is a non-classical major histocompatibility complex (MHC) protein, responsible for lipid antigen presentation, which presents lipids to natural killer T (NKT) cells. Various CD1d lipid ligands have been reported, including microbial and endogenous glycolipids/phospholipids. Among them, an α-galactosylceramide (α-GalCer), a representative CD1d ligand, is one of the most potent ligands and its derivatives have been developed. In this chapter, the chemistry of α-GalCer and its derivatives are described with an emphasis on their chemical syntheses and molecular interaction analysis with CD1d are described.

Placental macrophage responses to viral and bacterial ligands and the influence of fetal sex.

Bacterial and viral infections of the placenta are associated with inflammation and adverse pregnancy outcomes. Hofbauer cells (HBCs) are fetal-origin macrophages in the placenta, proposed to protect the fetus from vertical pathogen transmission. We performed quantitative proteomics on term HBCs under resting conditions and following exposure to bacterial and viral pathogen-associated molecular patterns (PAMPs), and investigated the contribution of fetal sex. Resting HBCs expressed proteins pertinent to macrophage function, including chemokines, cytokines, Toll-like receptors, and major histocompatibility complex class I and II molecules. HBCs mounted divergent responses to bacterial versus viral PAMPs but exhibited protein expression changes suggestive of a more pro-inflammatoryphenotype. A comparison between male and female HBCs showed that the latter mounted a stronger and wider response. Here, we provide a comprehensive understanding of the sex-dependent responses of placental macrophages to infectious triggers, which were primarily associated with lipid metabolism in males and cytoskeleton organization in females.

MICA Polymorphism and Genetic Predisposition to T1D in Jordanian Patients: A Case-Control Study.

Type 1 diabetes (T1D) is an autoimmune disorder whose etiology includes genetic and environmental factors. The non-classical Major Histocompatibility Complex (MHC) class I chain-related gene A (MICA) gene has been associated with increased susceptibility to T1D as the interaction of MICA to the Natural Killer Group 2D (NK2GD) receptors found on the cell surface of natural killer (NK) cells and T cells is responsible for inducing immune responses. MICA polymorphisms were reported in association with T1D among different ethnic groups. However, data from different populations revealed conflicting results, so the association of MICA polymorphisms with predisposition to T1D remains uncertain. The aim of this sequencing-based study was to identify, for the first time, the possible MICA alleles and/or genotypes that could be associated with T1D susceptibility in the Jordanian population. Polymorphisms in exons 2-4 and the short tandem repeats (STR) in exon 5 of the highly polymorphic MICA gene were analyzed. No evidence for association between T1D and MICA alleles/genotypes was found in this study, except for the MICA*011 allele which was found to be negatively associated with T1D (p = 0.023, OR = 0.125). In conclusion, MICA polymorphisms seem not to be associated with increasing T1D susceptibility in Jordanian patients.

The Role of Leukocyte Immunoglobulin-Like Receptors Focusing on the Therapeutic Implications of the Subfamily B2.

The leukocyte immunoglobulin (Ig)-like receptors (LILRs) are constituted by five inhibitory subpopulations (LILRB1-5) and six stimulatory subpopulations (LILRA1-6). The LILR populations substantially reside in immune cells, especially myeloid cells, functioning as a regulator in immunosuppressive and immunostimulatory responses, during which the nonclassical major histocompatibility complex (MHC) class I molecules are widely involved. In addition, LILRs are also distributed in certain tumor cells, implicated in the malignancy progression. Collectively, the suppressive Ig-like LILRB2 is relatively well-studied to date. Herein, we summarized the whole family of LILRs and their biologic function in various diseases upon ligation to the critical ligands, therefore providing more information on their potential roles in these pathological processes and giving the clinical significance of strategies targeting LILRs.

In vivo CRISPR screens reveal the landscape of immune evasion pathways across cancer.

The immune system can eliminate tumors, but checkpoints enable immune escape. Here, we identify immune evasion mechanisms using genome-scale in vivo CRISPR screens across cancer models treated with immune checkpoint blockade (ICB). We identify immune evasion genes and important immune inhibitory checkpoints conserved across cancers, including the non-classical major histocompatibility complex class I (MHC class I) molecule Qa-1b/HLA-E. Surprisingly, loss of tumor interferon-γ (IFNγ) signaling sensitizes many models to immunity. The immune inhibitory effects of tumor IFN sensing are mediated through two mechanisms. First, tumor upregulation of classical MHC class I inhibits natural killer cells. Second, IFN-induced expression of Qa-1b inhibits CD8+ T cells via the NKG2A/CD94 receptor, which is induced by ICB. Finally, we show that strong IFN signatures are associated with poor response to ICB in individuals with renal cell carcinoma or melanoma. This study reveals that IFN-mediated upregulation of classical and non-classical MHC class I inhibitory checkpoints can facilitate immune escape.

Human leukocyte antigen HLA-C, HLA-G, HLA-F, and HLA-E placental profiles are altered in early severe preeclampsia and preterm birth with chorioamnionitis

The extravillous trophoblast expresses each of the nonclassical major histocompatibility complex class I antigens-human leukocyte antigens E, F, and G-and a single classical class I antigen, human leukocyte antigen C. We recently demonstrated dynamic expression patterns of human leukocyte antigens C, G, and F during early extravillous trophoblast invasion and placentation. This study aimed to investigate the hypothesis that the immune inflammatory mediated complications of pregnancy such as early preeclampsia and preterm labor may show altered expression profiles of nonclassical human leukocyte antigens. Real-time quantitative polymerase chain reaction, western blot, and immunohistochemistry were performed on placental villous tissues and basal plate sections from term nonlaboring deliveries, preterm deliveries, and severe early-onset preeclampsia, both with and without small-for-gestational-age neonates. Human leukocyte antigen G is strongly and exclusively expressed by the extravillous trophoblast within the placental basal plate, and its levels increase in pregnancies complicated by severe early-onset preeclampsia with small-for-gestational-age neonates relative to those of healthy term controls. Human leukocyte antigen C shows a similar profile in the extravillous trophoblast of preeclamptic pregnancies, but significantly decreases in the villous placenta. Human leukocyte antigen F protein levels are decreased in both extravillous trophoblast and villous placenta of severe early-onset preeclamptic pregnancies, both with and without small-for-gestational-age neonates, compared with those found in term and preterm birth deliveries. Human leukocyte antigen E decreases in blood vessels in placentas from preeclamptic pregnancies relative to its levels in term and preterm birth deliveries. Placental levels of human leukocyte antigens F and C are increased in cases of preterm birth with chorioamnionitis relative to those of cases of idiopathic preterm birth. Dysregulation of placental human leukocyte antigen expression at the maternal-fetal interface may contribute to compromised maternal tolerance in preterm birth with chorioamnionitis and excessive maternal systemic inflammation associated with severe early-onset preeclampsia.

Biological Characteristics of HLA-G and Its Role in Solid Organ Transplantation.

Organ transplantation is a lifesaving option for patients with advanced diseases. Rejection is regarded as one of the most severe risk factors post-transplantation. A molecule that contributes to immune tolerance and resisting rejection is human leukocyte antigen (HLA)-G, which belongs to the non-classical major histocompatibility complex class (MHC) I family. HLA-G was originally found to play a role during pregnancy to maintain immune tolerance between mother and child. It is expressed in the placenta and detected in several body fluids as soluble factor as well as different membrane isoforms on cells. Recent findings on HLA-G show that it can also play multifaceted roles during transplantation. This review will explain the general characteristics and biological function of HLA-G and summarize the views supporting the tolerogenic and other roles of HLA-G to better understand its role in solid organ transplantation (SOT) and its complications. Finally, we will discuss potential future research on the role of HLA-G in prevention, diagnosis, and treatment in SOT.