Intrathecal synthesis of soluble HLA-G and HLA-I molecules are reciprocally associated to clinical and MRI activity in patients with multiple sclerosis

Investigating Serum sHLA-G Cooperation With MRI Activity and Disease-Modifying Treatment Outcome in Relapsing-Remitting Multiple Sclerosis

Relapsing-remitting multiple sclerosis (RRMS) is a demyelinating disease in which pathogenesis T cells have a major role. Despite the unknown etiology, several risk factors have been described, including a strong association with human leukocyte antigen (HLA) genes. Recent findings showed that HLA class I-G (HLA-G) may be tolerogenic in MS, but further insights are required. To deepen the HLA-G role in MS inflammation, we measured soluble HLA-G (sHLA-G) and cytokines serum level in 27 patients with RRMS at baseline and after 12 and 24 months of natalizumab (NTZ) treatment. Patients were divided into high (sHLA-G>20 ng/ml), medium (sHLA-G between 10 and 20 ng/ml), and low (sHLA-G <10 ng/ml) producers. Results showed a heterogeneous distribution of genotypes among producers, with no significant differences between groups. A significant decrease of sHLA-G was found after 24 months of NTZ in low producers carrying the +3142 C/G genotype. Finally, 83.3% of high and 100% of medium producers were MRI-activity free after 24 months of treatment, compared to 63.5% of low producers. Of note, we did not find any correlation of sHLA-G with peripheral cell counts or cytokines level. These findings suggest that serum sHLA-G level may partly depend on genotype rather than peripheral inflammation, and that may have impacted on MRI activity of patients over treatment.

IDO and Kynurenine Metabolites in Peripheral and CNS Disorders

The importance of the kynurenine pathway in normal immune system function has led to an appreciation of its possible contribution to autoimmune disorders such as rheumatoid arthritis. Indoleamine-2,3-dioxygenase (IDO) activity exerts a protective function, limiting the severity of experimental arthritis, whereas deletion or inhibition exacerbates the symptoms. Other chronic disorder with an inflammatory component, such as atherosclerosis, are also suppressed by IDO activity. It is suggested that this overall anti-inflammatory activity is mediated by a change in the relative production or activity of Th17 and regulatory T cell populations. Kynurenines may play an anti-inflammatory role also in CNS disorders such as Huntington's disease, Alzheimer's disease and multiple sclerosis, in which signs of inflammation and neurodegeneration are involved. The possibility is discussed that in Huntington's disease kynurenines interact with other anti-inflammatory molecules such as Human Lymphocyte Antigen-G which may be relevant in other disorders. Kynurenine involvement may account for the protection afforded to animals with cerebral malaria and trypanosomiasis when they are treated with an inhibitor of kynurenine-3-monoxygenase (KMO). There is some evidence that changes in IL-10 may contribute to this protection and the relationship between kynurenines and IL-10 in arthritis and other inflammatory conditions should be explored. In addition, metabolites of kynurenine downstream of KMO, such as anthranilic acid and 3-hydroxy-anthranilic acid can influence inflammation, and the ratio of these compounds is a valuable biomarker of inflammatory status although the underlying molecular mechanisms of the changes require clarification. Hence it is essential that more effort be expended to identify their sites of action as potential targets for drug development. Finally, we discuss increasing awareness of the epigenetic regulation of IDO, for example by DNA methylation, a phenomenon which may explain differences between individuals in their susceptibility to arthritis and other inflammatory disorders.

Study of Soluble HLA-G in Congenital Human Cytomegalovirus Infection

Human leukocyte antigen-G (HLA-G) is a nonclassical HLA class I antigen that is expressed during pregnancy contributing to maternal-fetal tolerance. HLA-G can be expressed as membrane-bound and soluble forms. HLA-G expression increases strongly during viral infections such as congenital human cytomegalovirus (HCMV) infections, with functional consequences in immunoregulation. In this work we investigated the expression of soluble (s)HLA-G and beta-2 microglobulin (component of HLA) molecules in correlation with the risk of transmission and severity of congenital HCMV infection. We analyzed 182 blood samples from 130 pregnant women and 52 nonpregnant women and 56 amniotic fluid samples from women experiencing primary HCMV infection. The median levels of sHLA-G in maternal serum of women with primary HCMV infection were higher in comparison with nonprimary and uninfected pregnant women (p < 0.001). AF from HCMV symptomatic fetuses presented higher sHLA-G levels in comparison with infected asymptomatic fetuses (p < 0.001), presence of HLA-G free-heavy chain, and a concentration gradient from amniotic fluid to maternal blood. No significant statistical difference of beta-2 microglobulin median levels was observed between all different groups. Our results suggest the determination of sHLA-G molecules in both maternal blood and amniotic fluid as a promising biomarker of diagnosis of maternal HCMV primary infection and fetal HCMV disease.

Serum IgG against Simian Virus 40 antigens are hampered by high levels of sHLA-G in patients affected by inflammatory neurological diseases, as multiple sclerosis

BACKGROUND

Many investigators detected the simian polyomavirus SV40 footprints in human brain tumors and neurologic diseases and recently it has been indicated that SV40 seems to be associated with multiple sclerosis (MS) disease. Interestingly, SV40 interacts with human leukocyte antigen (HLA) class I molecules for cell entry. HLA class I antigens, in particular non-classical HLA-G molecules, characterized by an immune-regulatory function, are involved in MS disease, and the levels of these molecules are modified according with the disease status.

OBJECTIVE

We investigated in serum samples, from Italian patients affected by MS, other inflammatory diseases (OIND), non-inflammatory neurological diseases (NIND) and healthy subjects (HS), SV40-antibody and soluble sHLA-G and the association between SV40-prevalence and sHLA-G levels.

METHODS

ELISA tests were used for SV40-antibodies detection and sHLA-G quantitation in serum samples.

RESULTS

The presence of SV40 antibodies was observed in 6 % of patients affected by MS (N = 4/63), 10 % of OIND (N = 8/77) and 15 % of NIND (N = 9/59), which is suggestive of a lower prevalence in respect to HS (22 %, N = 18/83). MS patients are characterized by higher sHLA-G serum levels (13.9 ± 0.9 ng/ml; mean ± St. Error) in comparison with OIND (6.7 ± 0.8 ng/ml), NIND (2.9 ± 0.4 ng/ml) and HS (2.6 ± 0.7 ng/ml) subjects. Interestingly, we observed an inverse correlation between SV40 antibody prevalence and sHLA-G serum levels in MS patients.

CONCLUSION

The data obtained showed a low prevalence of SV40 antibodies in MS patients. These results seems to be due to a generalized status of inability to counteract SV40 infection via antibody production. In particular, we hypothesize that SV40 immune-inhibitory direct effect and the presence of high levels of the immune-inhibitory HLA-G molecules could co-operate in impairing B lymphocyte activation towards SV40 specific peptides.

CD4(+)HLA-G(+) regulatory T cells: Molecular signature and pathophysiological relevance

The regulation of potentially harmful immune responses by regulatory T (Treg) cells is essential for maintaining peripheral immune tolerance and homeostasis. Especially CD4(+) Treg cells have been regarded as pivotal regulators of autoreactive and inflammatory responses as well as inducers of immune tolerance by using a variety of immune suppressive mechanisms. Besides the well-known classical CD4(+)CD25(+)FoxP3(+) Treg cells, CD4(+) T cells expressing the immune tolerizing molecule human leukocyte antigen G (HLA-G) have been recently described as another potent thymus-derived Treg (tTreg) cell subset. Albeit both tTreg subsets share common molecular characteristics, the mechanisms of their immunosuppressive function differ fundamentally. Dysfunction and numerical abnormalities of classical CD4(+) tTreg cells have been implicated in the pathogenesis of several immune-mediated diseases such as multiple sclerosis (MS). Clearly, a deeper understanding of the various CD4(+) tTreg subsets and also the underlying mechanisms of impaired immune tolerance in these disorders are essential for the development of potential therapeutic strategies. This review focuses on the current knowledge on defining features and functioning of HLA-G(+)CD4(+) tTreg cells as well as their emerging role in various pathologies with special emphasis on the pathogenesis of MS. Furthermore, future research possibilities together with potential therapeutic applications are discussed.

Cerebrospinal fluid amounts of HLA-G in dimeric form are strongly associated to patients with MRI inactive multiple sclerosis

Background:

The relevance of human leukocyte antigen (HLA)-G in dimeric form in multiple sclerosis (MS) is still unknown.

Objective:

To investigate the contribution of cerebrospinal fluid (CSF) HLA-G dimers in MS pathogenesis.

Methods:

CSF amounts of 78-kDa HLA-G dimers were measured by western blot analysis in 80 MS relapsing–remitting MS (RRMS) patients and in 81 inflammatory and 70 non-inflammatory controls.

Results:

CSF amounts of 78kDa HLA-G dimers were more frequent in RRMS than in inflammatory ( p<0.01) and non-inflammatory controls ( p<0.001) and in magnetic resonance imaging (MRI) inactive than in MRI active RRMS ( p<0.00001).

Conclusion:

Our findings suggest that HLA-G dimers may be implicated in termination of inflammatory response occurring in MS.

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.

The Role of HLA in MS Susceptibility and Phenotype

One of the most consistent findings in multiple sclerosis (MS) is that development of MS is linked with carriage of the class II human leucocyte antigen (HLA) molecule HLA-DRB1*15:01; around 60 % of Caucasian MS patients carry this allele compared to 25-30 % of ethnically matched healthy individuals. However, other HLA molecules have also been linked to the development of MS. In this chapter, the association between different HLA types and susceptibility to MS will be reviewed, and other linkages between the carriage of specific HLA molecules and clinical and experimental findings in MS will be considered.

HLA-G Molecules in Autoimmune Diseases and Infections

Human leukocyte antigen (HLA)-G molecule, a non-classical HLA-Ib molecule, is less polymorphic when compared to classical HLA class I molecules. Human leukocyte antigen-G (HLA-G) was first detected on cytotrophoblast cells at the feto-maternal interface but its expression is prevalent during viral infections and several autoimmune diseases. HLA-G gene is characterized by polymorphisms at the 3' un-translated region and 5' upstream regulatory region that regulate its expression and are associated with autoimmune diseases and viral infection susceptibility, creating an unbalanced and pathologic environment. This review focuses on the role of HLA-G genetic polymorphisms, mRNA, and protein expression in autoimmune conditions and viral infections.

Impact of HLA-G analysis in prevention, diagnosis and treatment of pathological conditions

Human leukocyte antigen-G (HLA-G) is a non-classical HLA class I molecule that differs from classical HLA class I molecules by low polymorphism and tissue distribution. HLA-G is a tolerogenic molecule with an immune-modulatory and anti-inflammatory function on both innate and adaptative immunity. This peculiar characteristic of HLA-G has led to investigations of its role in pathological conditions in order to define possible uses in diagnosis, prevention and treatment. In recent years, HLA-G has been shown to have an important implication in different inflammatory and autoimmune diseases, pregnancy complications, tumor development and aggressiveness, and susceptibility to viral infections. In fact, HLA-G molecules have been reported to alternate at both genetic and protein level in different disease situations, supporting its crucial role in pathological conditions. Specific pathologies show altered levels of soluble (s)HLA-G and different HLA-G gene polymorphisms seem to correlate with disease. This review aims to update scientific knowledge on the contribution of HLA-G in managing pathological conditions.

Intrathecal soluble HLA-E correlates with disease activity in patients with multiple sclerosis and may cooperate with soluble HLA-G in the resolution of neuroinflammation

Expression and function of the immunoregulatory molecule HLA-E was investigated in patients with relapsing-remitting (RR) multiple sclerosis (MS). Serum and cerebrospinal fluid (CSF) soluble (s)HLA-E and -G levels were measured by ELISA in 80 RRMS patients. Controls were patients with other inflammatory neurological disorders (OIND, n = 81) and noninflammatory neurological disorders (NIND, n = 86). Serum sHLA-E concentrations were higher in RRMS than in NIND patients only. CSF sHLA-E concentrations were higher in RRMS than controls. Increased CSF sHLA-E levels were detected in MRI inactive and clinically stable RRMS patients. sHLA-E intrathecal synthesis (ITS) was higher in RRMS than controls, and the number of patients with sHLA-E ITS above cut-off was higher i) in MS than controls, and ii) in clinically stable than clinically active MS patients. sHLA-E CSF levels and ITS correlated with i) the same sHLA-G parameters, and ii) disease duration. HLA-E expression and co-expression with CD markers were investigated in MS plaques from three different cases by immunohistochemistry and confocal microscopy, respectively. Infiltrating T lymphocytes and macrophages, as well as resident microglial cells and astrocytes expressed HLA-E. CSF samples from MS patients were finally tested for inhibitory activity of in vitro CTL and NK cell mediated cytotoxicity. sHLA-E⁺ were more effective than sHLA-E⁻ CSF samples in such inhibition. Maximum inhibition was achieved with sHLA-E⁺/sHLA-G⁺ CSF samples In conclusion, increased sHLA-E CSF levels may play an immunomodulatory role in MS, contributing to the inhibition of intrathecal inflammatory response. The potential of sHLA-E as biomarker of MS activity warrants further investigation.

Matrix metalloproteinase-2 (MMP-2) generates soluble HLA-G1 by cell surface proteolytic shedding

Human leukocyte antigen-G (HLA-G) molecules are non-classical HLA class I antigens with an important role in pregnancy immune regulation and inflammation control. Soluble HLA-G proteins can be generated through two mechanisms: alternative splicing and proteolytic release, which is known to be metalloprotease mediated. Among this class of enzymes, matrix metalloproteinases (MMPs) might be involved in the HLA-G1 membrane cleavage. Of particular interest are MMP-2 and MMP-9, which regulate the inflammatory process by cytokine and chemokine modulation. We evaluated the effect of MMP-9 and MMP-2 on HLA-G1 membrane shedding. In particular, we analyzed the in vitro effect of these two gelatinases on the secretion of HLA-G1 via proteolytic cleavage in 221-G1-transfected cell line, in JEG3 cell line, and in peripheral blood mononuclear cells. The results obtained by both cell lines showed the role of MMP-2 in HLA-G1 shedding. On the contrary, MMP-9 was not involved in this process. In addition, we identified three possible highly specific cleavage sites for MMP-2, whereas none were detected for MMP-9. This study suggests an effective link between MMP-2 and HLA-G1 shedding, increasing our knowledge on the regulatory machinery beyond HLA-G regulation in physiological and pathological conditions.

The expression of human leukocyte antigen G (HLA-G) is associated with sacroiliitis stages of ankylosing spondylitis

Recent studies have demonstrated that human leukocyte antigen G (HLA-G) may play an important role in autoimmune diseases. The present study is to investigate whether or not HLA-G is associated with sacroiliitis stages of ankylosing spondylitis (AS), a systemic autoimmune disease. Plasma levels of soluble HLA-G (sHLA-G) and HLA-G expression on the surface of peripheral blood mononuclear cells (PBMCs) were measured in 55 AS patients and 49 healthy controls by using a specific HLA-G ELISA and flow cytometric (FCM) analysis, respectively. Association of HLA-G expression with sacroiliitis stages of the patients was statistically analyzed. The plasma sHLA-G concentrations were noticeably lower in the AS patients when compared to the healthy controls while the mean fluorescence intensity (MFI) of the HLA-G expression on the surface of PBMCs was significantly higher in the AS patients than in the healthy controls (both P<0.0001). The HLA-G expression on the surface of PBMCs, plasma sHLA-G levels and HLA-B27 expression were significantly correlated to each other. Moreover, the plasma sHLA-G was inversely associated with the sacroiliitis stages (P=0.008), while the HLA-G expression on the surface of PBMCs increased from stage 0 to II but decreased in stage III (P=0.001). The significant association of HLA-G expressions with AS sacroiliitis stages suggests that HLA-G is possibly involved in the pathology of the disease. The detection of HLA-G expression may therefore be a useful laboratory test to reveal disease process in AS patients.

Role of HLA-G 14bp deletion/insertion and +3142C>G polymorphisms in the production of sHLA-G molecules in relapsing-remitting multiple sclerosis

HLA-G is believed to act as an anti-inflammatory molecule in Multiple Sclerosis (MS). The 3' untranslated region of the HLA-G gene is characterized by two polymorphisms, DEL/INS14bp and +3142C>G, which control soluble HLA-G (sHLA-G) production. The influence of these two HLA-G variants on sHLA-G serum and cerebrospinal fluid (CSF) levels was investigated in 69 Relapsing-Remitting MS patients grouped in magnetic resonance imaging (MRI) inactive and active disease. Serum and CSF sHLA-G levels were more elevated in high than in low DEL/INS 14bp and +3142C>G sHLA-G producers and were different among the various combined HLA-G genotypes in both MRI inactive and active diseases. The highest and the lowest sHLA-G values were identified in MS patients with C/C,DEL/DEL and G/G,INS/INS genotypes, respectively. Our preliminary findings suggest that serum and CSF sHLA-G levels in MS could be influenced by HLA-G polymorphisms irrespective of the inflammatory microenvironment.

Soluble HLA-G dampens CD94/NKG2A expression and function and differentially modulates chemotaxis and cytokine and chemokine secretion in CD56bright and CD56dim NK cells

Soluble HLA-G (sHLA-G) inhibits natural killer (NK) cell functions. Here, we investigated sHLA-G-mediated modulation of (1) chemokine receptor and NK receptor expression and function and (2) cytokine and chemokine secretion in CD56bright and CD56dim NK cells. sHLA-G-treated or untreated peripheral blood (PB) and tonsil NK cells were analyzed for chemokine receptor and NK receptor expression by flow cytometry. sHLA-G down-modulated (1) CXCR3 on PB and tonsil CD56bright and CD56dim, (2) CCR2 on PB and tonsil CD56bright, (3) CX3CR1 on PB CD56dim, (4) CXCR5 on tonsil CD56dim, and (5) CD94/NKG2A on PB and tonsil CD56brigh) and CD56dim NK cells. Such sHLA-G-mediated down-modulations were reverted by adding anti-HLA-G or anti-ILT2 mAbs. sHLA-G inhibited chemotaxis of (1) PB NK cells toward CXCL10, CXCL11, and CX3CL1 and (2) PB CD56bright NK cells toward CCL2 and CXCL10. IFN-γ secretion induced by NKp46 engagement was inhibited by NKG2A engagement in untreated but not in sHLA-G-treated NK cells. sHLA-G up-regulated secretion of (1) CCL22 in CD56bright and CD56dim and (2) CCL2, CCL8, and CXCL2-CXCL3 in CD56dim PB NK cells. Signal transduction experiments showed sHLA-G-mediated down-modulation of Stat5 phosphorylation in PB NK cells. In conclusion, our data delineated novel mechanisms of sHLA-G-mediated inhibition of NK-cell functions.

Involvement of kynurenines in Huntington's disease and stroke-induced brain damage

Several components of the kynurenine pathway of tryptophan metabolism are now recognised to have actions of profound biological importance. These include the ability to modulate the activation of glutamate and nicotinic receptors, to modify the responsiveness of the immune system to inflammation and infection, and to modify the generation and removal of reactive oxygen species. As each of these factors is being recognised increasingly as contributing to major disorders of the central nervous system (CNS), so the potentially fundamental role of the kynurenine pathway in those disorders is presenting a valuable target both for understanding the progress of those disorders and for developing potential drug treatments. This review will summarise some of the evidence for an important contribution of the kynurenines to Huntington's disease and to stroke damage in the CNS. Together with preliminary evidence from a study of kynurenine metabolites after major surgery, an important conclusion is that kynurenine pathway activation closely reflects cognitive function, and may play a significant role in cognitive ability.

Emerging topics and new perspectives on HLA-G

Following the Fifth International Conference on non-classical HLA-G antigens (HLA-G), held in Paris in July 2009, we selected some topics which focus on emerging aspects in the setting of HLA-G functions. In particular, HLA-G molecules could play a role in: (1) various inflammatory disorders, such as multiple sclerosis, intracerebral hemorrhage, gastrointestinal, skin and rheumatic diseases, and asthma, where they may act as immunoregulatory factors; (2) the mechanisms to escape immune surveillance utilized by several viruses, such as human cytomegalovirus, herpes simplex virus type 1, rabies virus, hepatitis C virus, influenza virus type A and human immunodeficiency virus 1 (HIV-1); and (3) cytokine/chemokine network and stem cell transplantation, since they seem to modulate cell migration by the downregulation of chemokine receptor expression and mesenchymal stem cell activity blocking of effector cell functions and the generation of regulatory T cells. However, the immunomodulatory circuits mediated by HLA-G proteins still remain to be clarified.

A major histocompatibility Class I locus contributes to multiple sclerosis susceptibility independently from HLA-DRB1*15:01

Background

In Northern European descended populations, genetic susceptibility for multiple sclerosis (MS) is associated with alleles of the human leukocyte antigen (HLA) Class II gene DRB1. Whether other major histocompatibility complex (MHC) genes contribute to MS susceptibility is controversial.

Methodology/Principal Findings

A case control analysis was performed using 958 single nucleotide polymorphisms (SNPs) spanning the MHC assayed in two independent datasets. The discovery dataset consisted of 1,018 cases and 1,795 controls and the replication dataset was composed of 1,343 cases and 1,379 controls. The most significantly MS-associated SNP in the discovery dataset was rs3135391, a Class II SNP known to tag the HLA-DRB1*15:01 allele, the primary MS susceptibility allele in the MHC (O.R. = 3.04, p<1×10⁻⁷⁸). To control for the effects of the HLA-DRB1*15:01 haplotype, case control analysis was performed adjusting for this HLA-DRB1*15:01 tagging SNP. After correction for multiple comparisons (false discovery rate = .05) 52 SNPs in the Class I, II and III regions were significantly associated with MS susceptibility in both datasets using the Cochran Armitage trend test. The discovery and replication datasets were merged and subjects carrying the HLA-DRB1*15:01 tagging SNP were excluded. Association tests showed that 48 of the 52 replicated SNPs retained significant associations with MS susceptibility independently of the HLA-DRB1*15:01 as defined by the tagging SNP. 20 Class I SNPs were associated with MS susceptibility with p-values ≤1×10⁻⁸. The most significantly associated SNP was rs4959039, a SNP in the downstream un-translated region of the non-classical HLA-G gene (Odds ratio 1.59, 95% CI 1.40, 1.81, p = 8.45×10⁻¹³) and is in linkage disequilibrium with several nearby SNPs. Logistic regression modeling showed that this SNP's contribution to MS susceptibility was independent of the Class II and Class III SNPs identified in this screen.

Conclusions

A MHC Class I locus contributes to MS susceptibility independently of the HLA-DRB1*15:01 haplotype.

Timing of serum soluble HLA-G levels in acute and subacute phases after spontaneous intracerebral hemorrhage

Serum levels of sHLA-G (sHLA-G1/HLA-G5) antigens and their soluble isoforms, sHLA-G1 and HLA-G5, were measured by ELISA in 22 patients with spontaneous intracerebral hemorrhage (SICH) at 24 h, 48 h and 7 days after bleeding. The perihematomal edema volume was calculated on non-enhanced computed tomography scans using the formula AxBxC/2 at the same time points. The mean serum concentrations of sHLA-G1/HLA-G5 and sHLA-G1 as well as the perihematomal edema volume changed significantly over time (p < 0.0001, p < 0.001 and p < 0.0001, respectively), whereas no statistical differences were found in serum HLA-G5 concentrations over the course of the experiment. In comparison to the values found at 24 h, sHLA-G1/HLA-G5 and sHLA-G1 increased at 48 h and then decreased at 7 days, whereas the perihematomal edema volume was more elevated at 48 h and, to a lesser extent, at 7 days. A positive correlation was detected between mean serum sHLA-G1/HLA-G5 and sHLA-G1 levels and perihematomal edema volume at 24 h (p < 0.02) and at 48 h (p < 0.01). Our results may indicate a role for sHLA-G in inflammatory mechanisms related to SICH, where these proteins probably act as anti-inflammatory molecules and are predominantly produced as the sHLA-G1 isoform.

Amniotic fluid soluble human leukocyte antigen-G in term and preterm parturition, and intra-amniotic infection/inflammation

OBJECTIVE

Circulating soluble human leukocyte antigen-G (sHLA-G) has been associated with pregnancy complications, and determination of sHLA-G concentrations in amniotic fluid (AF) has been reported in normal pregnancies. Our aim was to determine if the AF concentrations of sHLA-G change with advancing gestation, spontaneous labor at term, and in patients with spontaneous preterm labor (PTL) with intact membranes, as well as in those with preterm prelabor rupture of membranes (PROM), in the presence or absence of intra-amniotic infection/inflammation (IAI).

STUDY DESIGN

This cross-sectional study included the following groups: (1) mid-trimester (n = 55); (2) normal pregnancy at term with (n = 50) and without (n = 50) labor; (3) spontaneous PTL with intact membranes divided into: (a) PTL who delivered at term (n = 153); (b) PTL who delivered preterm without IAI (n = 108); and (c) PTL with IAI (n = 84); and (4) preterm PROM with (n = 46) and without (n = 44) IAI. sHLA-G concentrations were determined by ELISA. Non-parametric statistics were used for analysis.

RESULTS

(1) Among patients with PTL, the median AF sHLA-G concentration was higher in patients with IAI than in those without IAI or women that delivered at term (p < 0.001 for both comparisons); (2) Similarly, patients with preterm PROM and IAI had higher median AF sHLA-G concentrations than those without IAI (p = 0.004); (3) Among patients with PTL and delivery, those with histologic chorioamnionitis and/or funisitis had a higher median AF sHLA-G concentration than those without histologic inflammation (p < 0.001); and (4) The median AF sHLA-G concentration did not change with advancing gestational age.

CONCLUSIONS

AF sHLA-G concentrations are elevated in preterm parturition associated to IAI as well as in histologic chorioamnionitis. We propose that sHLA-G may participate in the regulation of the host immune response against intra-amniotic infection.

Genetic and epigenetic control of the major histocompatibility complex class Ib gene HLA-G in trophoblast cell lines

The transcriptional regulation of the major histocompatibility complex class (MHC) Ib gene HLA-G differs from the classical MHC class I genes. The cis-acting regulatory elements typical for classical MHC class I promoters are divergent in the promoter of HLA-G, rendering this gene unresponsive to NF-kappaB, IRF-1, and class II transactivator (CIITA)-mediated activation pathways. However, as we have previously shown, transactivation of HLA-G is regulated by CREB-1. Because CREB-1 is ubiquitously expressed, this observation does not explain the tissue-restricted expression of HLA-G in extravillous cytotrophoblasts. Using HLA-G-expressing JEG-3 cells and HLA-G-deficient JAR trophoblast-derived choriocarcinoma cells as a model, we have investigated the contribution of DNA methylation and histone acetylation in the transcriptional activation of HLA-G. Despite similar levels of DNA methylation both in JEG3 and JAR cells, we found the levels of histone acetylation in HLA-G promoter chromatin to be significantly enhanced in JEG3 cells coinciding with HLA-G expression.

Blood levels of kynurenines, interleukin-23 and soluble human leucocyte antigen-G at different stages of Huntington's disease

There is substantial evidence that abnormal concentrations of oxidised tryptophan metabolites, produced via the kynurenine pathway, contribute to progressive neurodegeneration in Huntington's disease. We have now examined the blood levels of these metabolites in patients at different stages of Huntington's disease, assessed both in terms of clinical disease severity and numbers of CAG repeats. Close relatives of the patients were included in the study as well as unrelated healthy controls. Levels of lipid peroxidation products, the pro-inflammatory cytokine interleukin (IL)-23 and the soluble human leucocyte antigen-G (sHLA-G) were also measured. There were lower levels of tryptophan and a higher kynurenine : tryptophan ratio, indicating activation of indoleamine-2,3-dioxygenase, in the most severely affected group of patients, with increased levels of IL-23 and sHLA-G. Marked correlations were noted between IL-23 and the patient severity group, anthranilic acid levels and the number of CAG repeats, and between anthranilic acid and IL-23, supporting our previous evidence of a relationship between anthranilic acid and inflammatory status. Tryptophan was negatively correlated with symptom severity and number of CAG repeats, and positively correlated with sHLA-G. The results support the proposal that tryptophan metabolism along the kynurenine pathway in Huntington's disease is related to the degree of genetic abnormality, to clinical disease severity and to aspects of immunopathogenesis.

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.

A functional role for soluble HLA-G antigens in immune modulation mediated by mesenchymal stromal cells

BACKGROUND

It has been suggested that soluble factors produced by bone marrow (BM) mesenchymal stromal cells (MSC) play a fundamental role in mediating immune modulation. HLA-G antigens (Ag) are major histocompatibility complex (MHC) class Ib molecules characterized by a limited polymorphism and a splicing mechanism that regulates the production of membrane-bound and soluble isoforms. Interleukin-10 (IL-10) cytokine is one of the main up-modulators of soluble HLA-G Ag (sHLA-G) production by CD14+ peripheral blood monocyte cells and increased IL-10 levels are reported to be associated with MSC immune modulation.

METHODS

We investigated, by specific enzyme-linked immunosorbent assay (ELISA), the possible role of sHLA-G molecules in the inhibition of the peripheral blood mononuclear cell (PBMC) response to phytohemagglutinin (PHA) mediated by MSC from different sources.

RESULTS

There was a significant correlation between the presence of increased levels of sHLA-G and IL-10 in the MSC/PBMC/PHA culture supernatants and lymphoproliferative inhibition. Neutralizing experiments performed with monoclonal Ab directed against HLA-G and IL-10 molecules confirmed the inhibitory ability of sHLA-G Ag. Furthermore, exogenous IL-10 induced sHLA-G molecule secretion by MSC alone in a polymorphic way, while a longitudinal analysis confirmed the loss of MSC inhibitory functions in relation to in vitro MSC aging.

DISCUSSION

Overall the results obtained suggest a functional role for sHLA-G molecules in inhibiting the PBMC response mediated by MSC. Moreover, the ability of IL-10 to induce sHLA-G Ag production by MSC alone could be proposed as a marker of MSC functional ability.

Soluble MHC class I chain-related protein B serum levels correlate with disease activity in relapsing-remitting multiple sclerosis

Recent studies demonstrated that dysregulation of NKG2D and its ligands, leading to activation of autoreactive effector cells, can trigger autoimmune diseases, but soluble forms of these ligands can downmodulate NKG2D expression in T effector cells. We investigated the presence of soluble major histocompatibility complex class I chain-related A or B (MICA or MICB) molecules in sera of multiple sclerosis (MS) patients and whether they play a role in the progression of the disease. Although soluble MICA serum levels did not differ, soluble MICB serum levels were higher in MS patients compared with controls. Moreover, the highest MICB levels were in MS patients during relapses. Using immunohistochemistry techniques, it was possible to locate MIC expression in neurons of MS demyelinating plaques that were intracellularly accumulated. Elevated soluble MICB levels exist in serum of multiple sclerosis patients related with disease activity. This may contribute to the modulation of immune response activity during relapses.

HLA-G: from biology to clinical benefits

The relevance of the nonclassical human leukocyte antigen (HLA) class I molecule HLA-G in human physiological and pathological contexts has been the center of intense investigation. In light of the recent advances, we report here the clinical implications of HLA-G as a tolerogenic molecule promoting uterine implantation of the embryo or acceptance of solid allografts while allowing the evasion of tumors or viruses from the immune response. These recent findings are important in terms of clinical benefits at both diagnostic and therapeutic levels.

CSF levels of soluble HLA-G and Fas molecules are inversely associated to MRI evidence of disease activity in patients with relapsing-remitting multiple sclerosis

Cerebrospinal fluid (CSF) concentrations of soluble human leukocyte antigen class I (HLA-I) (sHLA-I), HLA-G (sHLA-G) and anti-apoptotic Fas (sFas) molecules were measured by enzyme linked immunosorbent assay technique in 65 relapsing-remitting (RR) MS patients classified according to clinical and magnetic resonance imaging (MRI) evidence of disease activity. Sixty-four patients with other inflammatory neurological disorders (OIND) and 64 subjects with noninflammatory neurological disorders (NIND) served as controls. CSF concentrations were higher in RRMS and in OIND than in NIND patients for sHLA-I (P < 0.02), greater in RRMS than in OIND and in NIND for sHLA-G (P < 0.001 and P < 0.01, respectively) and lower in RRMS than in OIND and in NIND for sFas (P < 0.001 and P < 0.02, respectively). An increase in CSF levels was identified in MRI active RRMS for sHLA-I (P < 0.01) and in MRI stable RRMS for sHLA-G (P < 0.01), whereas CSF values of sFas were decreased in RRMS without Gd-enhancing lesions (P < 0.02). In MS patients with no evidence of MRI disease activity, a trend towards an inverse correlation was found between CSF concentrations of sHLA-G and sHLA-I and between CSF levels of sHLA-G and sFas. Our results indicate that enhanced CSF levels of sHLA-I antigens most likely represent an indirect manifestation of intrathecal immune activation taking place in neuroinflammation. Conversely, reciprocal fluctuations in CSF sHLA-G and sFas levels observed when MRI disease activity resolved suggest that sHLA-G could play an immunomodulatory role in MS through Fas/FasL-mediated mechanisms.

Soluble HLA-G molecules are released as HLA-G5 and not as soluble HLA-G1 isoforms in CSF of patients with relapsing-remitting multiple sclerosis

Cerebrospinal fluid (CSF) levels of sHLA-G (sHLA-G1/HLA-G5) molecules and their soluble isoforms HLA-G5 and sHLA-G1 were measured by ELISA procedures in 68 relapsing-remitting Multiple Sclerosis (RR MS) patients, in 67 patients with other inflammatory neurological disorders (OIND) and in 70 subjects with non-inflammatory neurological disorders (NIND). CSF concentrations of sHLA-G1/HLA-G5 and HLA-G5 were higher in RR MS than in OIND and NIND, and in Magnetic Resonance Imaging (MRI) inactive as compared to MRI active RR MS. Our results indicate that the potential implication of sHLA-G proteins in the resolution of MS intrathecal inflammatory response is probably due to HLA-G5 isoform.

14 bp deletion polymorphism in the HLA-G gene is a risk factor for idiopathic dilated cardiomyopathy in a Chinese Han population

Human leukocyte antigen (HLA) has been reported to be associated with the pathogenesis of autoimmune-associated idiopathic dilated cardiomyopathy (IDC). However, the HLA-G in this context is limited. In the current study, a total of 117 IDC patients and age and sex matched 401 unrelated healthy controls in a Chinese Han population were HLA-G genotyped for the 14 bp insertion and deletion polymorphism. IDC patients showed markedly increased frequencies of -14 bp/-14 bp genotype [Pc = 0.00049, odds ratio (OR) = 2.17] and -14 bp alleles (Pc = 4.1 x 10(-5), OR = 1.97) when compared with healthy controls. Whereas the frequencies of +14 bp/+14 bp genotype (Pc = 0.0036, OR = 0.35) and +14 bp alleles (Pc = 4.1 x 10(-5), OR = 0.51) were significantly lower in IDC. These data, for the first time, indicated that 14 bp insertion/deletion polymorphism in HLA-G gene could be a genetic risk factor for the susceptibility to IDC.

Soluble HLA-G: Are they clinically relevant?

HLA-G is a non-classical HLA-class Ib molecule with multiple immunoregulatory properties. Its main function in physiological conditions is to abrogate maternal NK cell activity against foetal tissue and to establish immune tolerance at maternal-foetal interface. HLA-G is expressed not only as a membrane bound molecule on the surface of cells, but also as a soluble moiety in body fluids. The major isoforms of HLA-G present in serum are soluble HLA-G1 and HLA-G5 which are generated by shedding or proteolytic cleavage of the membrane bound isoform and by secretion of a soluble isoform, respectively. Here we review the data about soluble HLA-G (sHLA-G) serum levels in different pathological conditions, including immune-mediated disorders, transplantation and malignancies. In particular, we focus on sHLA-G expression and function in human neuroblastoma, a pediatric tumor, with special emphasis on a novel potential immuno escape mechanism utilized by NB to instruct monocytes to produce and release sHLA-G. Finally, the potential clinical relevance of sHLA-G serum levels is discussed.

HLA‐DRB1*1501, ‐DQB1*0301, ‐DQB1*0302, ‐DQB1*0602, and ‐DQB1*0603 Alleles are Associated With More Severe Disease Outcome on Mri in Patients With Multiple Sclerosis

The most important confirmed genetic factor of susceptibility to multiple sclerosis (MS) has been identified in the HLA class II region. The hypothesis that several genes, including HLA class II, may influence the prognosis of patients with MS has been proposed. In a recent study, using low intermediate resolution typing, we found that some HLA alleles may predict disease severity as assessed by magnetic resonance imaging (MRI) measures. The aim of this study was to examine the relationship between high-resolution typing of HLA alleles and disease severity as measured by brain MRI quantitative markers of demyelinating and destructive pathology in patients with MS. In 41 MS patients (27 relapsing-remitting, 7 secondary progressive, and 7 primary progressive), we performed high-resolution typing of alleles HLA-DRB1*04, -DQB1*03, -DRB1*15, -DQB1*06, and of haplotypes -DRB1*04-DQB1*03 and -DRB1*15-DQB1*06. These alleles and haplotypes were associated with higher susceptibility to MS in a recently published case-control study conducted in the Friuli-Venezia-Giulia region, Italy. Of 41 included patients, 13 were men and 28 were women. Mean age was 43.3 (SD 11.4) years, mean disease duration 10.3 (SD 7.8) years, and mean EDSS 2.3. DNA extraction and genomic typing were obtained with the sequence-specific primers method using primer pairs that amplified the HLA alleles. All patients underwent a 1.5-T MRI examination of the brain. Disease severity was assessed by clinical measures [Expanded Disability Status Scale (EDSS)] and MRI measures. T2- and T1-lesion volumes (LVs) and brain atrophy measures [fractions of brain parenchyma (BPF), gray matter (GMF), and white matter (WMF)] were calculated. We used general linear model analysis (GML), controlled for age, disease duration, and treatment status, to compare the MRI measures according to allele and haplotype status. The following significant results were found: HLA-DRB1*1501 positive patients had significantly lower GMF (0.493 vs 0.526, p < 0.001), lower BPF (0.784 vs 0.815, p = 0.018), and higher T1-LV (2.8 vs 0.7ml, p = 0.036); -DQB1*0301 positive patients had significantly higher T2-LV (34.1 vs 0.7 ml, p = 0.041), and showed a trend for lower BPF (0.790 vs 0.846, p = 0.064); -DQB1*0302 positive patients had significantly lower T1-LV (2.4 vs 0.9 ml, p = 0.016); and -DQB1*0602 positive patients had significantly lower GMF (0.492 vs 0.521, p = 0.007) and lower BPF (0.781 vs 0.811, p = 0.023). No differences were found in the indices of MRI disease severity according to HLA haplotype associations. Both in correlation and in regression analyses, we observed significant associations between HLA-DRB1*1501 and lower GMF and BPF and higher T1-LV, between -DQB1*0301 and higher T2-LV and disease duration, between -DQB1*0302 and lower GMF and higher T1- and T2-LV, between -DQB1*0602 and lower GMF and BPF, and between -DQB1*0603 and higher T1-LV and EDSS. High-resolution HLA genotyping analysis revealed a robust relationship between alleles HLA-DRB1*1501, -DQB1*0301, -DQB1*0302, -DQB1*0602, and -DQB1*0603, and more severe damage on inflammatory and neurodegenerative MRI measures.