HLA-G and MIC expression in tumors and their role in anti-tumor immunity

Igniting cold tumors of intrahepatic cholangiocarcinoma: An insight into immune evasion and tumor immune microenvironment

<p>Intrahepatic cholangiocarcinoma (ICC) is a rare hepatobiliary cancer that originates from the epithelium of the intrahepatic bile duct. The various treatments for ICC, such as chemotherapy, radiotherapy, and locoregional therapy, confer only modest improvements in survival rates. Immunotherapy, although revolutionary in cancer treatment, has found limited application in the treatment of ICCs due to the “cold” nature of these tumors, which is marked by scant T-cell infiltration. This characteristic makes immune checkpoint inhibitors (ICIs) unsuitable for the majority of ICC patients. Therefore, comprehensively understanding the mechanisms underlying these “cold” tumors is crucial for harnessing the potential of immunotherapy for treating ICC patients. This paper explores immune evasion mechanisms and the complex tumor immune microenvironment of ICC. This study provides a comprehensive overview of therapeutic strategies aimed at activating cold tumors and enhancing their immunogenicity. Furthermore, potential and promising targets for cancer vaccines and adoptive cellular therapy in the context of ICC are discussed. This endeavor strives to reveal new pathways for innovative immunotherapy strategies, with a focus on overcoming the key challenge of triggering an effective immune response in ICC patients.</p>

Cross-Cancer Pleiotropic Analysis Reveals Novel Susceptibility Loci for Lung Cancer

Genome-wide association studies (GWASs) have identified hundreds of single nucleotide polymorphisms (SNPs) associated with cancer risk, several of which have shown pleiotropic effects across cancers. Therefore, we performed a systematic cross-cancer pleiotropic analysis to detect the effects of GWAS-identified variants from non-lung cancers on lung cancer risk in 12,843 cases and 12,639 controls from four lung cancer GWASs. The overall association between variants in each cancer and risk of lung cancer was explored using sequential kernel association test (SKAT) analysis. For single variant analysis, we combined the result of specific study using fixed-effect meta-analysis. We performed functional exploration of significant associations based on features from public databases. To further detect the biological mechanism underlying identified observations, pathway enrichment analysis were conducted with R package “clusterProfiler.” SNP-set analysis revealed the overall associations between variants of 8 cancer types and lung cancer risk. Single variant analysis identified 6 novel SNPs related to lung cancer risk after multiple correction (P_fdr < 0.10), including rs1707302 (1p34.1, OR = 0.93, 95% CI: 0.90–0.97, P = 7.60 × 10⁻⁴), rs2516448 (6p21.33, OR = 1.07, 95% CI: 1.03–1.11, P = 1.00 × 10⁻³), rs3869062 (6p22.1, OR = 0.91, 95% CI: 0.86–0.96, P = 7.10 × 10⁻⁴), rs174549 (11q12.2, OR = 0.90, 95% CI: 0.87–0.94, P = 1.00 × 10⁻⁷), rs7193541 (16q23.1, OR = 0.93, 95% CI: 0.90–0.96, P = 1.20 × 10⁻⁴), and rs8064454 (17q12, OR = 1.07, 95% CI: 1.03–1.11, P = 4.30 × 10⁻⁴). The eQTL analysis and functional annotation suggested that these variants might modify lung cancer susceptibility through regulating the expression of related genes. Pathway enrichment analysis showed that genes modulated by these variants play important roles in cancer carcinogenesis. Our findings demonstrate the pleiotropic associations between non-lung cancer susceptibility loci and lung cancer risk, providing important insights into the shared mechanisms of carcinogenesis across cancers.

NKG2D Polymorphism in Melanoma Patients from Southeastern Spain

Background: Natural killer (NK) and CD8+ T cells are involved in the immune response against melanoma. C-Type lectin-like NK cell receptors are located in the Natural Killer Complex (NKC) region 12p13.2-p12.3 and play a critical role in regulating the activity of NK and CD8+ T cells. An association between polymorphisms in the NKC region, including the NKG2D gene and NKG2A promoter, and the risk of cancer has been previously described. The aim of this study was to analyze the association of polymorphisms in the NKC region with cutaneous melanoma in patients from southeastern Spain. Methods: Seven single-nucleotide polymorphisms (SNPs) in the NKG2D gene (NKC3,4,7,9,10,11,12), and one SNP in the NKG2A promoter (NKC17) were genotyped by a TaqMan 5′ Nuclease Assay in 233 melanoma patients and 200 matched healthy controls. Results: A linkage disequilibrium analysis of the SNPs performed in the NKC region revealed two blocks of haplotypes (Hb-1 and Hb-2) with 14 and seven different haplotype subtypes, respectively. The third most frequent haplotype from the block Hb-2—NK3 (CAT haplotype)—was significantly more frequent on melanoma patients than on healthy controls (p = 0.00009, Pc = 0.0006). No further associations were found when NKC SNPs were considered independently. Conclusions: Our results suggest an association between NKG2D polymorphisms and the risk of cutaneous malignant melanoma.

Immunological status of chronically exposed persons with increased level of TCR mutations

Dose- and dose rate-dependent increase in the number of СD3⁺СD16⁺CD56⁺-lymphocytes and lysosomal activity of neutrophils was noted in peripheral blood of the Techa riverside residents with increased level of TCR gene-mutated T lymphocytes long after chronic exposure of predominantly red bone marrow (mean exposure dose was 0.89 ± 0.09 Gy, individual dose range was 0.09-1.96 Gy). The performed analysis showed that the above-mentioned immunological changes could be a response to an increase in the frequency of mutations (TCR mutations in particular) in the cells of exposed individuals.

Immunotherapy for acute myeloid leukemia (AML): a potent alternative therapy

The standard therapy of AML for many years has been chemotherapy with or without stem transplantation. However, there has not been any tangible improvement in this treatment beyond induction through chemotherapy and consolidation with allogeneic stem cell transplantation or chemotherapy. Residual AML cells which later cause relapse mostly persist even after rigorous standard therapy. It is imperative therefore to find an alternative therapy that can take care of the residual AML cells. With a better understanding of how the immune system works to destroy tumor cells and inhibit their growth, another therapeutic option immunotherapy has emerged to address the difficulties associated with the standard therapy. Identification of leukemia-associated antigens (LAA) and the fact that T and NK cells can be activated to exert cytotoxicity on AML cells have further introduced diverse immunotherapeutic development strategies. This review discusses the merits of current immunotherapeutic strategies such as the use of antibodies, adoptive T cells and alloreactive NK cell, and vaccination as against the standard therapy of AML.

Determination of HLA-G Expression and Evaluation of Its Role as a Prognostic Factor in Chronic Lymphocytic Leukemia

BACKGROUND

In recent years, the clinical and biological features governing the clinical course of chronic lymphocytic leukemia (CLL) have been most extensively studied. Human leukocyte antigen-G (HLA-G) allows tumor cells to escape from the antitumor effect of the immune system. Recent studies have shown that various tumor cells show an increased HLA-G expression. Data regarding HLA-G expression in CLL are limited and controversial. The aim of this work is to evaluate flow cytometry study of HLA-G expression on cell surface and assess its relationship with other prognostic factors (CD38, ZAP70, beta 2 microglobulin [β2MG]) in patients with CLL.

DESIGN AND METHODS

Forty-five newly diagnosed CLL cases. White blood cell count, lymphocyte absolute count, hemoglobin level, platelet count, serum lactate dehydrogenase activity, and serum β2MG level were studied at admission. In each patient, morphologic diagnosis of B-CLL was confirmed by flow cytometry HLA-G, CD38 and ZAP70 expression levels were measured with four-color flow cytometry.

RESULTS

HLA-G positivity ranged between 1% and 12% in CLL patients. A significant correlation was found with CD38, ZAP70, disease stage, and β2MG (P < 0.001). The off-treatment follow-up period was longer in the HLA-G negative group (P < 0.022).

CONCLUSIONS

In conclusion, we suggest that, in addition to other prognostic factors, surface HLA-G expression can be considered as an independent prognostic factor. However, our work should be confirmed by further prospective studies, a longer off-treatment follow-up period, and a standardized method.

Analysis of Il-10 gene sequence in patients with sinonasal polyposis

Sinonasal polyposis (SNP) is a chronic inflammatory disease of nasal and paranasal cavities. Human leukocyte antigen-G molecules (HLA-G) are non-classic HLA-I molecules with anti-inflammatory and tolerogenic properties. HLA-G production is mainly induced by interleukin (IL)-10. IL-10 is an anti-inflammatory cytokine that inhibits the production of proinflammatory cytokines and induces HLA-class II down-modulation. Recent studies suggest that HLA-G could play a role in SNP pathogenesis; in SNP patients physiological levels of IL-10 (produced by activated peripheral blood CD14+ monocytes) are not able to induce production of HLA-G. Different mechanisms could justify these findings: genomic or amino-acidic sequence alterations in IL-10 lower IL-10 receptor expression, lower IL-10 receptor affinity, or alterations of the intracellular signal transmission. This study analyzes nucleotidic sequence of IL-10 gene in SNP patients. Sequencing of IL-10 gene shows that the lack of HLA-G production by peripheral blood CD14+ monocytes is not related to alterations in IL-10 gene nucleotidic sequence.

MHC class I chain-related gene a diversity in patients with cutaneous malignant melanoma from southeastern Spain

A limited number of studies have been performed so far on the polymorphism in the transmembrane region (exon 5) of the major histocompatibility complex class I chain-related gene A (MICA) in patients with melanoma. However, the influence of MICA polymorphism in extracellular domains (exons 2, 3, and 4) has not been investigated on melanoma disease. This study aims to characterize the influence of extracellular MICA polymorphism, and its previously described linkage disequilibrium with HLA-B locus, on patients with cutaneous melanoma from southeastern Spain. For this purpose, MICA and HLA-B genotyping was performed in 233 patients and 200 ethnically matched controls by luminex technology. Patients were classified according to the presence of methionine or valine at codon 129 of MICA gene. We found a high frequency of MICA^*009 in melanoma patients compared with controls (P = 0.002, Pc = 0.03). Our results also showed an association between MICA^*009 and HLA-B^*51 alleles in both patients and controls. This association was stronger in patients than controls (P = 0.015). However, a multivariate logistic regression model showed that neither MICA^*009 nor the combination MICA^*009/HLA-B^*51 was associated with melanoma susceptibility. No relationship was observed between MICA-129 dimorphism and melanoma nor when MICA polymorphism was evaluated according to clinical findings at diagnosis.

The clinicopathologic significance of the expression of HLA-G in oral squamous cell carcinoma

OBJECTIVE

This study aimed to evaluate HLA-G expression in primary oral cavity squamous cell carcinoma (OCSCC) and potentially malignant lesions and to evaluate its relationship with clinicopathologic parameters.

STUDY DESIGN

HLA-G expression in samples from patients with metastatic and nonmetastatic OCSCC (n = 60), potentially malignant lesions (n = 15), and clinically and histologically normal oral mucosa (n = 10) was characterized by immunohistochemistry. The density of CD8, CD83, and CD68 cells and Ki-67(+) and bcl-2(+) neoplastic cells were analyzed.

RESULTS

HLA-G expression by neoplastic cells was significantly higher in metastatic OCSCC compared with nonmetastatic OCSCC (P = .01). Higher HLA-G expression was observed in OCSCC than in potentially malignant lesions (P = .006). Moreover, patients with lower HLA-G expression exhibited a tendency toward longer survival (22 months) compared with those with higher HLA-G expression (16 months).

CONCLUSIONS

Our findings suggest that increased HLA-G expression in metastatic OCSCC may represent a tumor escape mechanism, which portends an unfavorable clinical prognosis.

Transmission of "split anergy" from tumor infiltrating to peripheral NK cells in a manner similar to "infectious tolerance"

According to a new paradigm of carcinogenesis, a tumor arises not from transformed cell, but only from tumor initiating cells called cancer stem cells (CSCs), which can originate from tissue stem cells. CSC are resistant to conventional therapy and after treatment form new tumors and give rise to metastases. Only natural killer (NK) cells are capable of lysing CSCs, but within different tumor types these cells experience a condition known as "split anergy", whereby the NK cells lose the ability to kill CSCs and being to produce cytokines. As a result, uncontrolled tumor growth arises and tumor stroma accumulates anergic NK cells. We hypothesize that anergic tumor infiltrating NK (TINK) cells transmit their property to naïve NK cells by infecting" them with a state of "split anergy" in a similar manner as T conventional cells are transformed into T regulatory cells during the process of "infectious tolerance". Anergic TINK cells egress from the tumor stroma via the lymphatic system, where they reach regional lymph nodes and transmit their properties to naïve NK cells, which in turn become anergic toward CSCs and lose immunosurveillance functions. The mechanisms proposed for this hypothesis and the methodological approaches for confirming the idea are presented in this issue.

Human iPS cell-derived hematopoietic progenitor cells induce T-cell anergy in in vitro-generated alloreactive CD8(+) T cells

Human induced pluripotent stem cells (iPSCs) have emerged as an alternative source of pluripotent stem cells that can be used for tissue regeneration in place of the controversial human embryonic stem cells. However, immunologic knowledge about iPSC derivatives remains enigmatic. Here, we characterized human iPS-derived CD34(+) hematopoietic progenitor cells (HPCs). These HPCs poorly express major histocompatibility complex (MHC) I antigens and are MHC-II negative. Interestingly, they moderately express nonclassical HLA-G and HLA-E molecules. Consequently, alloreactive HLA-A2-specific cytotoxic T cells failed to recognize HLA-A2-expressing HPCs but became anergic. Subsequent upregulation of MHC-I using interferon-γ stimulation and provision of CD28 cosignaling led to T-cell activation, confirming that poor delivery of signals 1 and 2 by the HPCs mediated T-cell anergy. These data indicate for the first time that HPCs induce T-cell anergy, a unique characteristic of iPSC-derived cells that confers immunologic advantage for allogenic transplantation. Although iPSCs are ideal for patient-tailored treatments with the anticipation that no immunosuppression will be required, in cases of gene defects, their derivatives could be used to treat diseases in nonhistocompatible recipients.

LINE1 family member is negative regulator of HLA-G expression

Class Ia molecules of human leucocyte antigen (HLA-A, -B and -C) are widely expressed and play a central role in the immune system by presenting peptides derived from the lumen of the endoplasmic reticulum. In contrast, class Ib molecules such as HLA-G serve novel functions. The distribution of HLA-G is mostly limited to foetal trophoblastic tissues and some tumour tissues. The mechanism required for the tissue-specific regulation of the HLA-G gene has not been well understood. Here, we investigated the genomic regulation of HLA-G by manipulating one copy of a genomic DNA fragment on a human artificial chromosome. We identified a potential negative regulator of gene expression in a sequence upstream of HLA-G that overlapped with the long interspersed element (LINE1); silencing of HLA-G involved a DNA secondary structure generated in LINE1. The presence of a LINE1 gene silencer may explain the limited expression of HLA-G compared with other class I genes.

Expression of human leukocyte antigen G is associated with prognosis in nasopharyngeal carcinoma

Human leukocyte antigen G (HLA-G) has multiple immune regulatory functions including the induction of immune tolerance in malignancies. The roles of HLA-G have not been investigated in nasopharyngeal carcinoma (NPC). This study is aimed to evaluate the role of HLA-G as prognostic factor for NPC patients as well as its role in the immune regulation. Western assays showed high HLA-G expression in NPC cell lines, but low in the immortalized nasopharyngeal epithelial cell line NP69. HLA-G protein was further detected in 79.2% of 552 NPC specimens with immunohistochemistry (IHC), but not in normal nasopharyngeal epithelium tissue. Moreover, high expression of HLA-G predicted poor survival of NPC patients and positively correlated with tumor N classification and recurrence or metastasis. Multivariate analysis indicated that HLA-G was an independent and unfavorable prognostic factor. Furthermore, the presence of CD68+ macrophages and IL-10 were also examined, which are two prognostic markers of NPC and important factors for regulating immune surveillance. The correlations of HLA-G with these two immune factors were revealed in NPC tissues. Taken together, our results suggest that HLA-G is an independent biomarker for NPC prognosis, and HLA-G might contribute to NPC progression, which might jointly regulate immune surveillance in NPC together with macrophages and IL-10.

Human papillomavirus immunization is associated with increased expression of different innate immune regulatory receptors

Human papillomavirus (HPV) is able to inhibit the secretion of gamma interferon (IFN-γ) and the expression of some immune innate cell receptors. Immunoglobulin-like transcript 2 (ILT2) is a regulatory receptor that seems to participate in the pathogenesis of viral infections. We have studied the expression and function of ILT2 and the expression of other NK cell receptors in 23 healthy women before and after immunization with the quadrivalent HPV (type 6/11/16/18) vaccine (Gardasil). Receptor expression was analyzed by flow cytometry in freshly isolated peripheral blood mononuclear cells as well as after in vitro stimulation with the quadrivalent HPV (type 6/11/16/18) vaccine. In addition, the regulatory function of ILT2 on cell proliferation and IFN-γ production was analyzed. We found a significant increase in the expression of ILT2 by NK and CD3(+) CD56(+) lymphocytes and monocytes after quadrivalent HPV (type 6/11/16/18) vaccine immunization. In addition, the in vitro stimulation with the quadrivalent HPV (type 6/11/16/18) vaccine also increased the proportion of CD3(-) CD56(+) ILT2(+) NK cells. Although the inhibitory function of ILT2 on cell proliferation was enhanced after HPV immunization, the in vitro engagement of this receptor did not affect the synthesis of IFN-γ induced by HPV. Finally, a significant increase in the expression of NKG2D, NKp30, and NKp46 by NK and CD3(+) CD56(+) lymphocytes was detected after quadrivalent HPV (type 6/11/16/18) vaccine immunization. Our data indicate that HPV immunization is associated with significant changes in the expression and function of different innate immune receptors, including ILT2, which may participate in the protective effect of HPV vaccines.

Efficient association analysis between colorectal cancer and allelic polymorphisms of HLA-DQB1 by comparison of age of onset

Common methods for identifying cancer-related genes are solely based on differences between gene frequencies in the disease and control groups, and do not take into account the age of onset in the gene carriers. In the present investigation, we developed a new study design based on the age of onset of cancer for the identification of colorectal cancer-related genes. The samples from patients with colorectal cancer were typed using an HLA-DQB1 polymerase chain reaction using a sequence-specific primers (PCR-SSP) typing kit. The mean age of subjects with and without the alleles was calculated. The mean age of subjects with the HLA-DQB1*02 allele was significantly less than that of subjects without this allele (p<0.05). We found that the HLA-DQB1*02 allele was associated with colorectal cancer susceptibility. This new method of analysis may therefore be an efficient and reliable approach for the identification of cancer-causing genes.

Global expression profiling of peripheral Qa-1-restricted CD8αα+TCRαβ+ regulatory T cells reveals innate-like features: implications for immune-regulatory repertoire

Among peripheral regulatory T cells, CD8(+) T cells also play an important role in the maintenance of immune homeostasis. A subset of CD8(+) Treg that express αβ T cell receptor (TCR) and CD8αα homodimers can recognize TCR-derived peptides in the context of the class Ib MHC molecule Qa-1. To gain a better understanding of the nature and phenotype of CD8αα(+)TCRαβ+ Treg, a global gene expression profiling using microarray, real-time quantitative polymerase chain reaction, and flow-cytometric analysis was performed using functional Treg clones and lines. The study findings show that CD8(+) Treg shared gene profile expressed by innate-like lymphocytes, including murine intraepithelial lymphocytes and thymic CD8αα(+)TCRαβ+ T-cell populations. In addition, this subset displays differential expression of several key regulatory molecules, including CD200. CD8αα(+) Treg expressed higher levels of a number of natural killer cell-related receptors and molecules belonging to the TNF superfamily. Collectively, peripheral class Ib-reactive CD8αα(+)TCRαβ+ T cells represent a unique regulatory population different from class Ia major histocompatibility complex-restricted conventional T cells. These studies have important implications for the regulatory mechanisms mediated by the CD8(+) Treg population in general.

Serum soluble HLA-E in melanoma: a new potential immune-related marker in cancer

BACKGROUND

Tumor-derived soluble factors, including soluble HLA molecules, can contribute to cancer immune escape and therefore impact on clinical course of malignant diseases. We previously reported that melanoma cells produce, in vitro, soluble forms of the non-classical MHC class I molecule HLA-E (sHLA-E). In order to investigate sHLA-E production by various tumors and to address its potential value as a tumor-associated marker, we developed a specific ELISA for the quantification of sHLA-E in biological fluids.

METHODOLOGY/PRINCIPAL FINDINGS

We developed a sHLA-E specific and sensitive ELISA and we showed that serum sHLA-E levels were significantly elevated (P<0.01) in melanoma patients (n = 127), compared with healthy donors (n = 94). sHLA-E was also detected in the culture supernatants of a wide variety of tumor cell lines (n = 98) including melanomas, kidney, colorectal and breast cancers. Cytokines regulation of sHLA-E production by tumor cells was also carried out. IFN-γ, IFN-α and TNF-α were found to upregulate sHLA-E production by tumor cells.

CONCLUSIONS/SIGNIFICANCE

In view of the broad tumor tissue release of HLA-E and its up-regulation by inflammatory cytokines, sHLA-E should be studied for its involvement in immune responses against tumors. Interestingly, our results demonstrated a positive association between the presence of serum sHLA-E and melanoma. Therefore, the determination of sHLA-E levels, using ELISA approach, may be investigated as a clinical marker in cancer patients.

Expression of HLA-G in patients with hepatocellular carcinoma

BACKGROUND

Human leukocyte antigen G (HLA-G) is a non-classical major histocompatibility complex class I molecule that has multiple immune regulatory functions including the induction of immune tolerance. The detection of HLA-G expression might serve as a clinical marker in the prediction of clinical outcomes for certain types of carcinoma. Currently, we investigated whether or not HLA-G is also expressed in patients with hepatocellular carcinoma (HCC), and whether the expression has clinical value.

METHODS

Serum levels of secreted HLA-G (sHLA-G) were measured by ELISA in 36 patients with HCC, 25 patients with liver cirrhosis (LC) and 25 healthy individuals. The expression of HLA-G in liver tissue was further studied using Western blotting in 36 patients with HCC and 25 with LC. The correlations between HLA-G status and various clinicopathological parameters including survival were analyzed.

RESULTS

The ELISA assay showed that the serum levels of sHLA-G in the HCC, LC and healthy groups were 132.6+/-31.4, 63.5+/-22.1, and 47.0+/-15.5 U/ml, respectively. Analysis of variance was used for inter-group comparison and differences were found between the HCC group and the other two groups (both P<0.01), while no difference was found between the LC group and the healthy group (P=0.112). HLA-G protein expression in liver tissue was found in 66.7% (24/36) of the primary sites of HCC, but not in benign lesions (LC). Further, the HLA-G expression in tumors had no significant correlation with the parameters of age, gender, histological grade and alpha-fetoprotein level. However, patients with HLA-G-positive tumors had a shorter postoperative survival time than those with HLA-G-negative tumors (P=0.014). Also, univariate analysis showed that HLA-G was an independent prognostic factor.

CONCLUSION

Our results indicated that the expression of HLA-G was a characteristic feature of HCC and patients with positive expression of HLA-G in malignant liver tissue had a poor prognosis.

Enhanced presentation of MHC class Ia, Ib and class II-restricted peptides encapsulated in biodegradable nanoparticles: a promising strategy for tumor immunotherapy

BACKGROUND

Many peptide-based cancer vaccines have been tested in clinical trials with a limited success, mostly due to difficulties associated with peptide stability and delivery, resulting in inefficient antigen presentation. Therefore, the development of suitable and efficient vaccine carrier systems remains a major challenge.

METHODS

To address this issue, we have engineered polylactic-co-glycolic acid (PLGA) nanoparticles incorporating: (i) two MHC class I-restricted clinically-relevant peptides, (ii) a MHC class II-binding peptide, and (iii) a non-classical MHC class I-binding peptide. We formulated the nanoparticles utilizing a double emulsion-solvent evaporation technique and characterized their surface morphology, size, zeta potential and peptide content. We also loaded human and murine dendritic cells (DC) with the peptide-containing nanoparticles and determined their ability to present the encapsulated peptide antigens and to induce tumor-specific cytotoxic T lymphocytes (CTL) in vitro.

RESULTS

We confirmed that the nanoparticles are not toxic to either mouse or human dendritic cells, and do not have any effect on the DC maturation. We also demonstrated a significantly enhanced presentation of the encapsulated peptides upon internalization of the nanoparticles by DC, and confirmed that the improved peptide presentation is actually associated with more efficient generation of peptide-specific CTL and T helper cell responses.

CONCLUSION

Encapsulating antigens in PLGA nanoparticles offers unique advantages such as higher efficiency of antigen loading, prolonged presentation of the antigens, prevention of peptide degradation, specific targeting of antigens to antigen presenting cells, improved shelf life of the antigens, and easy scale up for pharmaceutical production. Therefore, these findings are highly significant to the development of synthetic vaccines, and the induction of CTL for adoptive immunotherapy.

Implications of the polymorphism of HLA-G on its function, regulation, evolution and disease association

The HLA-G gene displays several peculiarities that are distinct from those of classical HLA class I genes. The unique structure of the HLA-G molecule permits a restricted peptide presentation and allows the modulation of the cells of the immune system. Although polymorphic sites may potentially influence all biological functions of HLA-G, those present at the promoter and 3′ untranslated regions have been particularly studied in experimental and pathological conditions. The relatively low polymorphism observed in the MHC-G coding region both in humans and apes may represent a strong selective pressure for invariance, whereas, in regulatory regions several lines of evidence support the role of balancing selection. Since HLA-G has immunomodulatory properties, the understanding of gene regulation and the role of polymorphic sites on gene function may permit an individualized approach for the future use of HLA-G for therapeutic purposes.

Biology of HLA-G in cancer: a candidate molecule for therapeutic intervention?

Although the expression of the non-classical HLA class I molecule HLA-G was first reported to be restricted to the fetal-maternal interface on the extravillous cytotrophoblasts, the distribution of HLA-G in normal tissues appears broader than originally described. HLA-G expression was found in embryonic tissues, in adult immune privileged organs, and in cells of the hematopoietic lineage. More interestingly, under pathophysiological conditions HLA-G antigens may be expressed on various types of malignant cells suggesting that HLA-G antigen expression is one strategy used by tumor cells to escape immune surveillance. In this article, we will focus on HLA-G expression in cancers of distinct histology and its association with the clinical course of diseases, on the underlying molecular mechanisms of impaired HLA-G expression, on the immune tolerant function of HLA-G in tumors, and on the use of membrane-bound and soluble HLA-G as a diagnostic or prognostic biomarker to identify tumors and to monitor disease stage, as well as on the use of HLA-G as a novel therapeutic target in cancer.

IL-2-activated haploidentical NK cells restore NKG2D-mediated NK-cell cytotoxicity in neuroblastoma patients by scavenging of plasma MICA

NK group 2D (NKG2D)-expressing NK cells exhibit cytolytic activity against various tumors after recognition of the cellular ligand MHC class I chain-related gene A (MICA). However, release of soluble MICA (sMICA) compromises NKG2D-dependent NK-cell cytotoxicity leading to tumor escape from immunosurveillance. Although some molecular details of the NKG2D-MICA interaction have been elucidated, its impact for donor NK (dNK) cell-based therapy of solid tumors has not been studied. Within an ongoing phase I/II trial, we used allogeneic IL-2 activated dNK cells after haploidentical stem cell transplantation for immunotherapy of patients with high-risk stage IV neuroblastoma. NKG2D levels on activated dNK cells increased strongly when compared with freshly isolated dNK cells and correlated with enhanced NK-cell cytotoxicity. Most importantly, elevated sMICA levels in patients plasma correlated significantly with impaired dNK-cell-mediated cytotoxicity. This effect could be reversed by high-dose infusion of activated dNK cells, which display high levels of surface NKG2D. Our data suggest that the provided excess of NKG2D leads to clearance of sMICA and preserves cytotoxicity of dNK cells via non-occupied NKG2D. In conclusion, our results identify this tumor immune escape mechanism as a target to improve immunotherapy of neuroblastoma and presumably other tumors.

Ionizing radiation modulates the surface expression of human leukocyte antigen-G in a human melanoma cell line

Human leukocyte antigen G (HLA-G) is a nonclassical HLA class I molecule involved in fetus protection from the maternal immune system, transplant tolerance, and viral and tumoral immune escape. Tumor-specific HLA-G expression has been described for a wide variety of malignancies, including melanomas. The aim of this study was to evaluate whether ionizing radiation (IR) could modulate the surface expression of HLA-G1 in a human melanoma cell line that expresses endogenously membrane-bound HLA-G1. For this purpose, cells were exposed to increasing doses of gamma-irradiation (0-20 Gy) and HLA-G1 levels at the plasma membrane were analyzed at different times postirradiation by flow cytometry. HLA-G total expression and the presence of the soluble form of HLA-G1 (sHLA-G1) in the culture medium of irradiated cells were also evaluated. IR was capable of downregulating cell surface and total HLA-G levels, with a concomitant increase of sHLA-G1 in the medium. These results could indicate that gamma-irradiation decreases HLA-G1 surface levels by enhancing the proteolytic cleavage of this molecule.

Xenopus, a unique comparative model to explore the role of certain heat shock proteins and non-classical MHC class Ib gene products in immune surveillance

The heat shock proteins (HSPs) gp96 and hsp70 can elicit potent anti-tumor responses and as such have significant clinical potential. Besides cytotoxic CD8 T cell (CTLs) effectors, evidence suggests that natural killer (NK) cells and other less well-characterized cell types also play a critical role in HSP-mediated anti-tumor responses. Owing to their high degree of phylogenetic conservation, we have proposed that HSPs are ancestral agents of immune surveillance; and postulated that their immunological properties, if important, should have been conserved during evolution. We are investigating this issue using a unique non-mammalian comparative tumor-immunity model in the frog Xenopus, which allows us to focus on the relationship between HSPs, classical MHC class Ia, and non-classical MHC class Ib molecules. In addition to a transplantable lymphoid tumor in genetically defined cloned Xenopus, we are generating transgenic frogs with inducible or knocked-down (RNAi) gene expression.

An six-amino acid motif in the alpha3 domain of MICA is the cancer therapeutic target to inhibit shedding

Expression of the MHC class I chain related molecules A and B (MICA/B) on tumor cell surface can signal the immune receptor NKG2D for tumor immune destruction. However, MIC was found to be shed by tumors in cancer patients, which negatively regulates host immunity and promotes tumor immune evasion and progression. The mechanisms by which tumors shed MIC are not well understood although diverse groups of enzymes are suggested to be involved. The functional complexity of these enzymes makes them unfeasible therapeutic targets for inhibiting MIC shedding. Here we identified an six-amino acid (6-aa) motif in the alpha3 domain of MIC that is critical for the interaction of MIC with ERp5 to enable shedding. Mutations in this motif prevented MIC shedding but did not interfere with NKG2D-mediated recognition of MIC. Our study suggests that the 6-aa motif is a feasible target to inhibit MIC shedding for cancer therapy.

Human leukocyte antigen class I expression is an independent prognostic factor in advanced ovarian cancer resistant to first-line platinum chemotherapy

Background:

Loss of HLA class I is important in ovarian cancer prognosis but its role as a prognostic indicator in relation to therapy remains unproven. We studied the prognostic potential of this antigen and its significance in relation to platinum therapy.

Methods:

A total of 157 primary ovarian cancers were assessed for HLA class I immunohistochemically and linked to a comprehensive database of clinicopathological variables, treatment details, and platinum sensitivity.

Results:

Tumours expressing high levels of HLA class I had significantly improved survival (P=0.044). There was a 19-month difference in the median overall survival between tumours with high and low antigen expression. HLA class I antigen expression, stage, and platinum sensitivity were independently predictive of prognosis on multivariate analysis. HLA class I antigen was shown to be expressed at higher levels in patients with good overall survival in platinum-resistant patients (P=0.042). HLA class I significantly correlated with overall survival on multivariate analyses (P=0.034).

Conclusion:

Low-level HLA class I expression is an independent prognostic indicator of poor clinical outcome in ovarian cancer. The survival advantage of patients with platinum-resistant tumours expressing high levels of HLA class I suggests that immunotherapy may be of use in these ovarian cancers resistant to standard chemotherapy.

Expression of the ULBP ligands for NKG2D by B-NHL cells plays an important role in determining their susceptibility to rituximab-induced ADCC

Antibody-dependent cellular cytotoxicity (ADCC) is a major antitumor mechanism of action of therapeutic monoclonal antibodies (mAbs). The aim of this study was to identify tumor-associated factors which determine susceptibility to rituximab-induced ADCC. Thirty different CD20+ non-Hodgkin lymphoma cell lines were phenotyped for characteristics such as level of expression of NKG2D ligands, and the influence thereof on susceptibility to rituximab-induced ADCC was established. The present study demonstrated that tumor cell susceptibility to rituximab-induced ADCC was determined by 3 major tumor-associated factors: (i) the amount of the target molecule, CD20; (ii) the amount of the ligands for inhibitory killer Ig-like receptors, major histocompatibility complex class I; and (iii) the amounts of some of the NKG2D ligands, especially UL16-binding protein (ULBP) 1-3. The importance of the ULBPs was confirmed using antibody blockade. In conclusion, this is the first report to show the importance for rituximab-induced ADCC of ULBPs expressed on tumor cells. The ULBPs could be valuable diagnostic biological markers and significant targets for immunotherapy to improve efficacy not only of rituximab but also of other therapeutic mAbs.

Novel nonclassical MHC class Ib genes associated with CD8 T cell development and thymic tumors

In jawed vertebrates, the heterogeneous nonclassical MHC class Ib (class Ib) gene family encodes molecules structurally similar to classical MHC class Ia (class Ia) but with more limited tissue distribution and lower polymorphism. In mammals, class Ib gene products are involved in stress responses, malignancy and differentiation of intrathymic CD8 T cells. The frog Xenopus laevis possesses at least 20 class Ib genes (XNCs), and 9 subfamilies have been defined so far. We have characterized two novel subfamilies, XNC10 and XNC11. XNC10 is phylogenetically and structurally distinct from both class Ia and other XNC genes. Besides thymic lymphoid tumors, XNC10 is preferentially expressed by circulating T cells and thymocytes of the CD8 lineage both in adult and in larvae from the onset of thymus organogenesis. XNC11 is expressed only by thymocytes and upregulated by several thymic lymphoid tumors. These data provide the first evidence of the expression of any class Ib genes in Xenopus larvae, and suggests evolutionary relationships between certain class Ib genes, malignancy and CD8 T cell ontogeny.

Molecular genetics of the swine major histocompatibility complex, the SLA complex

The swine major histocompatibility complex (MHC) or swine leukocyte antigen (SLA) complex is one of the most gene-dense regions in the swine genome. It consists of three major gene clusters, the SLA class I, class III and class II regions, that span approximately 1.1, 0.7 and 0.5Mb, respectively, making the swine MHC the smallest among mammalian MHC so far examined and the only one known to span the centromere. This review summarizes recent updates to the Immuno Polymorphism Database-MHC (IPD-MHC) website (http://www.ebi.ac.uk/ipd/mhc/sla/) which serves as the repository for maintaining a list of all SLA recognized genes and their allelic sequences. It reviews the expression of SLA proteins on cell subsets and their role in antigen presentation and regulating immune responses. It concludes by discussing the role of SLA genes in swine models of transplantation, xenotransplantation, cancer and allergy and in swine production traits and responses to infectious disease and vaccines.

Expression of HLA-G and MICA mRNA in renal allograft

HLA-G is a nonclassical MHC class I antigen that displays tolerogenic functions; MICA is a stress-regulated molecule recognized by NKG2D cytotoxicity-activating receptor expressed by NK and T cells subsets. We evaluated HLA-G isoforms and MICA mRNA levels in peripheral blood mononuclear cells (PBMCs) and in biopsies from kidney allograft recipients with acute rejection (AR), chronic rejection (CR), and stable graft evolution (SE). HLA-G1 was the only transcript resulted from amplification, both in PBMCs as in biopsy samples. HLA-G1 mRNA levels in PBMCs from 9/10 patients with CR, 7/9 with AR and 8/10 healthy volunteers were below the median value of SE patients. The analysis of biopsies revealed that patients with AR (n=6), who overcame rejection had a tendency towards higher HLA-G1 levels than those with nephrotoxic acute tubular necrosis (ATN) (n=3). Similar levels of MICA expression were observed in PBMCs from AR, CR, SE and C groups; MICA expression levels were similar also in biopsy specimens from AR and nephrotoxic ATN patients. No correlation was found between MICA expression and the graft state. These preliminary results suggest that HLA-G1 isoforms, but not MICA mRNA levels, may provide a marker for measuring the state of kidney allograft, and be the basis for further studies that may establish the influence of these molecules in renal allograft rejection or acceptance.

Decreased production of human leukocyte antigen G molecules in sinonasal polyposis

BACKGROUND

Sinonasal polyposis (SNP) is a chronic inflammatory pathology of nasal and paranasal cavities. Human leukocyte antigen (HLA) G molecules are nonclassic class I antigens with anti-inflammatory and tolerogenic properties. As most theories consider polyps to be the manifestation of chronic inflammation, there could be a possible implication of HLA-G molecules in SNP. The purpose of this study was to investigate the possible correlation between SNP and the production of soluble HLA-G (sHLA-G) by peripheral blood mononuclear cells (PBMCs).

METHODS

The study involved 22 SNP patients (11 with no evidence of disease [NED] after surgery and 11 with relapse [RE]) and 20 healthy subjects. The presence of sHLA-G in PBMC lipopolysaccharide (LPS)-stimulated culture supernatants was analyzed. The levels of interleukin (IL) 10, one of the main up-regulators of sHLA-G production, were determined. Exogenous IL-10 was added to the SNP PBMC cultures to reconstitute the impairment in sHLA-G production.

RESULTS

Increased IL-10 levels in LPS-activated PBMC culture supernatants were found in NED patients in comparison with healthy subjects (p = 0.0184). No sHLA-G production was observed in either of the patient subgroup supernatants (p < 0.0001). The addition of exogenous IL-10 showed the reconstitution of sHLA-G production in NED and in a lower amount in RE patients.

CONCLUSION

The results show a defect in sHLA-G production in SNP patients mainly related to the IL-10/HLA-G pathway. Given the anti-inflammatory functions of HLA-G molecules, this impairment could increase the susceptibility to the disease. The different sHLA-G production after exogenous IL-10 addition between NED and RE SNP could represent a marker of disease severity.

Tumor escape mechanisms: potential role of soluble HLA antigens and NK cells activating ligands

The crucial role played by human leukocyte antigen (HLA) antigens and natural killer (NK)-cell-activating ligands in the interactions of malignant cells with components of the host's immune system has stimulated interest in the characterization of their expression by malignant cells. Convincing evidence generated by the immunohistochemical staining of surgically removed malignant lesions with monoclonal antibodies recognizing HLA antigens and NK-cell-activating ligands indicates that the surface expression of these molecules is frequently altered on malignant cells. These changes appear to have clinical significance because in some types of malignant disease they are associated with the histopathological characteristics of the lesions as well as with disease-free interval and survival. These associations have been suggested to reflect the effect of HLA antigen and NK-cell-activating ligand abnormalities on the interactions of tumor cells with antigen-specific cytotoxic T lymphocytes (CTL) and with NK cells. Nevertheless, there are examples in which disease progresses in the face of appropriate HLA antigen and/or NK-cell-activating ligand as well as tumor antigen expression by malignant cells and of functional antigen-specific CTL in the investigated patient. In such scenarios, it is likely that the tumor microenvironment is unfavorable for CTL and NK cell activity and contributes to tumor immune escape. Many distinct escape mechanisms have been shown to protect malignant cells from immune recognition and destruction in the tumor microenvironment. In this article, following the description of the structural and functional characteristics of soluble HLA antigens and NK-cell-activating ligands, we will review changes in their serum level in malignant disease and discuss their potential role in the escape mechanisms used by tumor cells to avoid recognition and destruction.

HLA-G genotype and HLA-G expression in systemic lupus erythematosus: HLA-G as a putative susceptibility gene in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease mainly mediated by the deposit of immune complexes and defects in T lymphocytes and antigen-presenting cells along with a high production of T-helper 2 cytokines. A tolerance-inducible function of nonclassical class Ib human leukocyte antigen (HLA)-G molecule in innate and adaptive cellular responses has been reported, suggesting a role in inflammatory diseases. A 14 bp sequence insertion/deletion polymorphism (rs16375) in the 3'-untranslated region of the HLA-G gene has been associated to the stability of HLA-G messenger RNA. The insertion of the 14 bp sequence seems to be associated with lower levels of soluble HLA-G (sHLA-G). The aim of this study was to evaluate the possible association of the presence of the 14 bp sequence (+14 bp) with SLE. We have HLA-G genotyped 200 SLE patients and 451 healthy control subjects (HS; Italian) and analyzed the plasma levels of sHLA-G and interleukin-10 (IL-10) in a subset of SLE patients and healthy subjects (Italian and Danish). A significant increase of the +14 bp HLA-G allele was detected in the Italian SLE patients compared with HS [P = 0.003, OR 1.44 (95% CI 1.13-1.82)]. A significant increased frequency of HLA-G +14/+14 bp and a decreased frequency of HLA-G -14/-14 bp were observed in SLE patients. There median concentration of sHLA-G was significantly lower in the plasma of SLE patients compared with that in the plasma of healthy controls (P < 0.0001). Furthermore, the results confirmed higher concentrations of IL-10-positive plasma in SLE patients. These results support a potential role for HLA-G in the susceptibility of SLE.

Non-classical major histocompatibility complex proteins as determinants of tumour immunosurveillance

Tumours develop in vertebrate organisms endowed with immune systems that are potentially able to eradicate them. Nevertheless, our ever-increasing understanding of the complex interactions between lymphocytes and tumour cells fuels the long-standing hope of developing efficient immunotherapies against cancer. This review focuses on a versatile family of proteins, the major histocompatibility complex class Ib, which has been recently implicated in both the establishment of anti-tumour immune responses and in tumour immune response evasion. We focus on a subset of class Ib proteins, human leukocyte antigen (HLA)-G, Qa-2, CD1d and NKG2D ligands, which bind to either stimulatory or inhibitory receptors expressed on T, natural killer (NK) and NKT lymphocytes, and thereby modulate their anti-tumour activity.

Different production of soluble HLA-G antigens by peripheral blood mononuclear cells in ulcerative colitis and Crohn's disease: a noninvasive diagnostic tool?

BACKGROUND

HLA-G antigens are nonclassical major histocompatibility complex (MHC) class I molecules characterized by tolerogenic and antiinflammatory properties. Recently, a different expression of HLA-G antigens has been observed between intestinal biopsies of ulcerative colitis (UC) and Crohn's disease (CD) patients. These data suggested a functional role for HLA-G molecules in the diseases and proposed the HLA-G modulation as a marker for the diagnosis of UC and CD. The soluble HLA-G antigens (sHLA-G) are circulating molecules mainly produced by activated peripheral blood CD14+ monocytes.

METHODS

We tested, by specific enzyme-linked immunosorbent assay (ELISA), the sHLA-G molecule levels in the supernatants of unstimulated and bacterial lipopolysaccharide (LPS)-stimulated cultures of peripheral blood mononuclear cells (PBMC) from 30 healthy subjects, 10 CD, and 18 UC patients. The data were not influenced by treatment or disease activity.

RESULTS

The results confirmed a different sHLA-G expression between the diseases, with a spontaneous secretion of sHLA-G in CD patients but not in UC and healthy subjects. Moreover, a lack of sHLA-G antigens has been reported in UC patient cultures after LPS activation but not in healthy subjects and CD patients. The defective sHLA-G production was related to an impaired IL-10 secretion in UC but not in CD.

CONCLUSIONS

Overall, these results confirm the presence of a different biological characteristic between CD and UC patients and suggest sHLA-G production by PBMC as a noninvasive diagnostic tool in the early phases of the diseases.

Absence of the HLA-G*0105N allele in Amerindian populations from the Brazilian Amazon Region: a possible role of natural selection

The human leukocyte antigen G (HLA-G) null allele (G*0105N) is defined by a DeltaC deletion at exon 3. Its high frequency in populations from areas with high pathogen loads and the putative role of HLA-G in placental development suggest that the reduced G1 expression in G*0105N heterozygous placentas may improve the intrauterine defense against infections. The G*0105N allele frequencies were evaluated in 143 Amerindians from six isolated tribes that inhabit the Central Amazon to determine the existence of genotype frequencies that suggest balancing selection in favor of G*0105N heterozygotes. No copy of the null allele was found by exon 3 sequencing. Although this finding may be because of demographic or other selective factors, it also suggests no evidence of G*0105N heterozygous advantage.

Involvement of nonclassical MHC class Ib molecules in heat shock protein-mediated anti-tumor responses

Nonclassical MHC class Ib (class Ib) genes are found in all jawed vertebrates, and their products are hypothesized to be indicators of intracellular stress and malignancy. They may be involved in immune recognition of classical MHC class Ia (class Ia)-low or -negative tumor cells through their interaction with T cell receptors and/or non-T cell inhibitory or triggering receptors expressed by NK cells and T cells. In the frog Xenopus, the molecular chaperone gp96 mediates a potent immune response involving antigen-specific classical class Ia-unrestricted CD8+ CTL (CCU-CTL) against a transplantable thymic tumor (15/0) that does not express class Ia molecules. We hypothesized that Xenopus nonclassical class Ib gene products (XNC) are involved in gp96-mediated CCU-CTL anti-tumor responses. To investigate the involvement of class Ib gene products in Xenopus anti-tumor responses, we generated, for the first time in ectothermic vertebrates, stable tumor transfectants expressing short hairpin RNA (shRNA) to silence either XNC directly or beta2m to prevent class Ib surface expression. Both types of 15/0 transfectants are more resistant to CCU-CTL killing, more tumorigenic and more susceptible to NK-like cell killing. This study provides in vitro and in vivo evidence of the evolutionary conservation of class Ib involvement in anti-tumor CD8+ T cell responses.

Structure, expression and function of HLA-G in renal cell carcinoma

Tumors have developed different strategies to escape from immune cell recognition which include the downregulation or loss of the classical HLA class I antigens as well as aberrant expression of non-classical HLA antigens like HLA-G. Abnormalities in MHC class surface expression have also been described in renal cell carcinoma (RCC) and represent mechanisms to avoid elimination by immune effector cells. We here review the structure/polymorphism, mRNA and protein expression profile of HLA-G in RCC and corresponding normal kidney epithelium, its mode of regulation and its functional consequences on immune responses. A heterogeneous constitutive HLA-G mRNA and/or protein expression was found in both RCC lesions and RCC cell lines, whereas normal kidney epithelium totally lack HLA-G mRNA and protein expression. In comparison to other tumor entities, the frequency of HLA-G expression is relatively high in RCC. Since HLA-G expression is lost during cultivation of RCC cells, the tumor microenvironment and/or endothelium appear to be involved in the regulation of HLA-G expression in this disease. HLA-G expression could be transcriptionally upregulated in RCC by interferons, IL-10 and gangliosides. Silencing of HLA-G expression in RCC is often associated with methylation of the HLA-G promoter which could be reverted by the treatment with demethylating agents. Functional studies using natural killer cells, lymphokine activated killer cells as well as antigen-specific CD8+ cytotoxic T lymphocytes demonstrated that HLA-G expression prevents lysis of RCC cells by these different immune effector cells. In contrast, HLA-G-negative normal kidney cells as well as HLA-G-negative RCC cells were not recognized by NK and T cells. Thus, HLA-G represents one important immune escape mechanism of human RCC which has an impact on the design of T and NK cell-based immunotherapies in this disease.

Expression of Human Leukocyte Antigen G (HLA-G) Correlates with Poor Prognosis in Gastric Carcinoma

OBJECTIVE

We had previously demonstrated that human leukocyte antigen G (HLA-G) was expressed in a majority of primary colorectal carcinomas and that the detection of HLA-G expression had a strong and independent prognostic value for that cancer. Currently, we investigate whether or not HLA-G is also expressed in patients with gastric carcinoma and whether the expression has any clinical application value.

METHODS

The expression of HLA-G was investigated immunohistochemically in 160 patients with gastric carcinoma. The correlation between HLA-G status and various clinicopathological parameters was analyzed with the levels of HLA-G expression used to compare the survival length amongst patients.

RESULTS

HLA-G protein expression was observed in 71% (113 of 160) of the primary site of gastric carcinomas, but not in the normal stomach tissues. HLA-G expression in the tumors was significantly correlated with the tumor location, histological grade, depth of invasion, lymph nodal metastasis, clinical stages of the disease, and host immune response (P = .012, .008, .001, .038, .030, and .016, respectively). Patients with HLA-G positive tumors had a significantly shorter survival time than those patients with tumors that were HLA-G negative (P = .001). As well, in multivariate analysis, HLA-G demonstrated an independent prognostic factor (P = .0001, relative risk 9.08; 95% confidence interval, 3.44-24.0).

CONCLUSIONS

Overall, our results indicated that the expression of HLA-G is a characteristic feature of gastric carcinoma and that immunostaining by anti-HLA-G antibody may be a potentially useful prognostic indicator.

HLA-G 14-bp polymorphism regulates the methotrexate response in rheumatoid arthritis

OBJECTIVE

Methotrexate (MTX) represents the antirheumatic drug mainly used in rheumatoid arthritis (RA). HLA-G antigens are inducible nonclassical major histocompatibility complex class Ib molecules important for maintaining anti-inflammatory conditions. The HLA-G gene is characterized by a deletion/insertion polymorphism of 14 bp that controls specific mRNA stability and protein levels. It has been reported that MTX therapy mediates an increase of interleukin-10-producing cells. This cytokine up-regulates HLA-G expression. For this, we tested the hypothesis of an MTX-mediated HLA-G production and the possible relationship with the HLA-G 14-bp polymorphism.

METHODS

Peripheral blood mononuclear cells from healthy individuals and non-MTX-treated RA patients were activated with different MTX concentrations, and soluble HLA-G (sHLA-G) and interleukin-10 production was investigated by specific immunoenzymatic assay. HLA-G 14-bp polymorphism genotyping was performed in healthy individuals and RA patients, defined as 'responders' and 'nonresponders' to the MTX therapy.

RESULTS

MTX activation induces the production of sHLA-G molecules. A significant association was observed between the highest sHLA-G1 concentrations and the -14/-14 bp genotype. The analysis of the HLA-G 14-bp polymorphism in MTX-treated RA patients has confirmed an increase of the -14/-14 bp genotype in the responder group (chi=6.12, P=0.02; chi test) (odds ratio=2.46 (95% confidence interval, 1.26-4.84) P=0.009; logistic regression model).

CONCLUSION

Our results propose that the MTX induces the production of the anti-inflammatory sHLA-G molecules that concur with the therapy response. Furthermore, the association between -14/-14 bp genotype and MTX clinical outcome proposes this polymorphism as a therapy marker in the early phases of the disease.

Soluble HLA-G promotes Th1-type cytokine production by cytokine-activated uterine and peripheral natural killer cells

Soluble forms of HLA-G (sHLA-G) have been implicated in immune regulation. Fetal trophoblast cells are a prime source of HLA-G. Hence, an interaction between sHLA-G and uterine lymphocytes in the decidual tissues can easily be envisaged. These lymphocytes, when properly activated, are implicated in successful trophoblast invasion, placental maturation and maintenance of pregnancy. However, so far, no data are available on the effect of sHLA-G on the function and phenotype of these cells. Herein, we used a recombinant sHLA-G construct to determine the effect of sHLA-G on uterine lymphocyte cells present in endometrium at the time that it is optimally receptive to trophoblast invasion. In addition, we ascertained the effect of sHLA-G on peripheral lymphocytes. We found that upon co-culture with sHLA-G, proliferation of unfractionated IL-15-stimulated uterine mononuclear cells (UMCs) was inhibited. However, sHLA-G increased both interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha production by these cells. Vascular endothelial growth factor (VEGF) production was reduced. Notably, in contrast to membrane-bound HLA-G, sHLA-G did not affect the natural cytolytic activity of UMCs. Similarly, sHLA-G inhibited proliferation but stimulated pro-inflammatory cytokine production by cytokine-activated, unfractionated peripheral blood mononuclear cells (PBMCs). In addition, we showed that the overall inhibitory effect of sHLA-G on proliferation of the whole cell population could be ascribed to selective inhibition of CD4(+) T cells. In contrast, sHLA-G induced proliferation and IFN-gamma production by both uterine and peripheral natural killer (NK) cells. In conclusion, our data show that the sHLA-G modulates both UMC and PBMC function. sHLA-G, by promoting IFN-gamma production by uterine NK cells, may contribute to vascular remodelling of spiral arteries to allow for successful embryo implantation.

Retinoblastoma: expression of HLA-G

PURPOSE

Human leukocyte antigen (HLA) mediates interactions of tumor cells with cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells. Retinoblastoma (RB) is the most common intraocular malignant tumor in childhood and is characterized by direct spread to the optic nerve and orbit as well as hematogenous and lymphatic spread. Earlier, we observed that invasive RB showed reduced HLA, which could contribute to its escape from the immune system. Little is known about the role of the nonclassical HLA molecule, HLA-G, in RB and its role in tumor escape mechanisms in RB.

METHODS

Forty archival paraffin-embedded RB tumors were analyzed for the expression of HLA-G by immunohistochemistry using a monoclonal antibody; fresh tumor samples were also subjected to Western blot analysis. There were 22 tumors with no invasion and 18 with invasion of the choroid/optic nerve. Immunoanalysis was performed based on the International Histocompatibility Working Group Project Description.

RESULTS

HLA-G was negative in the non-neoplastic retina, reduced in 22/22 tumors with no invasion, and positive in 15/18 with invasion. The immunohistochemistry results were confirmed by Western blot analysis. The difference in expression between the two groups was significant ( p < 0.001). There was no correlation of HLA-G expression with differentiation of the tumors.

CONCLUSION

Increased expression of HLA-G was observed in invasive RB. This preliminary observation deserves further investigation and may shed more light on the immune escape mechanisms of this tumor and thus enable novel therapeutic strategies.