Soluble HLA-DR antigen levels in serum correlate with rheumatoid arthritis disease activity and the presence of disease-associated epitopes

Soluble HLA-I and HLA-II Molecules Are Potential Prognostic Markers of Progression of Systemic and Local Inflammation in Patients with COPD

Soluble molecules of the major histocompatibility complex play an important role in the development of various immune-mediated diseases. However, there is not much information on the participation of these proteins in the pathogenesis of chronic obstructive pulmonary disease (COPD). The aim of our work was to determine the content of soluble molecules of the major histocompatibility complex of classes I and II (sHLA-I and sHLA-II) in the exhaled breath condensate (EBC) and in the blood serum in patients with moderate to severe COPD during the exacerbation and stable phase. We investigated 105 patients (male) with COPD aged 46-67 and 21 healthy nonsmoking volunteers (male) comparable in age. The content of sHLA-I and sHLA-II molecules was studied using ELISA. We found an increase in the level of sHLA-I and sHLA-II molecules in EBC, as well as an enhancement in the serum content of sHLA-II in all the examined COPD patients compared to healthy nonsmoking volunteers. The revealed negative correlation between the serum concentration of sHLA-II and values of FEV1 and FEV1/FVC in all examined patients with COPD gives a possibility to consider the content of these proteins as an additional systemic marker of disease severity. The maximum endobronchial and serum concentrations of sHLA-I and sHLA-II were detected in patients with severe COPD during the exacerbation. The negative associations between the content of these molecules in EBC and serum and the parameters of lung function in patients with severe COPD were established. These findings suggest a pathogenetic role of sHLA-I and sHLA-II molecules in the mechanisms of the development and progression of local and systemic inflammation in COPD.

Soluble MHC class II-driven therapy for a systemic lupus erythematosus murine experimental in vitro and in vivo model

Taking into consideration the multiparametric nature of systemic lupus erythematosus (SLE), the severity and variability of symptoms and the lack of effective therapeutic approaches, this study took advantage of the recently described role of soluble major histocompatibility complex class II (sMHCII) molecules in maintaining tolerance to the organism and attempted to apply sMHCII proteins as a treatment to murine SLE experimental models in vitro as well as in vivo. After breaking tolerance to DNA in vitro, which was accompanied by development of specific anti-dsDNA antibodies, syngeneic or allogeneic sMHCII molecules, purified from healthy mouse serum, could significantly reduce the specific antibody levels and drive the system towards immunosuppression, as assessed by specific marker analysis on T cells and cytokine production by flow cytometry and ELISA, respectively. The in vivo experimental model consisted of pristane-induced SLE symptoms to BALB/c mice, which developed maximal levels of anti-dsDNA 2 months after pristane inoculation. Syngeneic or allogeneic sMHCII administration could alleviate pristane-induced symptoms, significantly decrease specific anti-dsDNA antibody production and develop immunosuppression to the host, as manifested by increase of CD4 + CTLA-4 +  and CD4 + CD25 +  cell populations in the spleen. Thus, the results presented in this study introduced the ability of sMHCII proteins to suppress specific autoantigen response, opening new areas of research and offering novel therapeutic approaches to SLE with expanding features to other autoimmune diseases.

Soluble HLA-DR serum levels are associated with smoking but not with acute coronary syndrome

BACKGROUND & AIMS

Elevated soluble HLA-DR (sHLA-DR) serum levels have been reported in HLA class II-associated inflammatory disorders. We have previously shown that the HLA class II allele HLA-DRB1*01 may predispose to acute coronary syndromes (ACS). To our knowledge, sHLA-DR serum levels have not been studied in ACS.

METHODS

sHLA-DR serum levels were measured in 477 ACS patients as cases and 475 area- and sex-matched controls by sandwich enzyme-linked immunosorbent assay. Binary logistic regression and ordinal logistic regression analyses adjusted for clinical parameters were conducted to evaluate the associations of sHLA-DR levels.

RESULTS

ACS patients had lower sHLA-DR serum levels compared to controls (OR = 0.837; 95% CI = 0.704-0.994; p = 0.043). After adjustment for smoking status, this association was no longer significant. This was explained by the notion that current smoking was inversely associated with sHLA-DR levels both in cases (OR = 0.592; 95% CI = 0.553-0.908; p = 0.016) and in controls (OR = 0.356; 95% CI = 0.226-0.563; p = 0.000010). A similar effect was not seen with other cardiovascular risk factors.

CONCLUSIONS

The results indicate, for the first time, that lower sHLA-DR levels are associated with smoking, but not with ACS. This is an important finding because previous studies of sHLA-DR have not accounted for the possible associations between smoking and sHLA-DR levels. Further studies are required to confirm these novel results and explore the mechanisms behind the observed associations.

Soluble MHC-II proteins promote suppressive activity in CD4+ T cells

Soluble MHCII (sMHCII) molecules are present in body fluids of healthy individuals and are considered to be involved in the maintenance of self tolerance, and are also related to various diseases. Their concentration increases during in vivo antigen-specific tolerogenic stimulation and it was recently shown that exosome-mediated tolerance is MHCII dependent. At the cellular level, sMHCII proteins compete with membrane MHCII for T-cell receptor binding on CD4(+) T cells. Immunoaffinity purification techniques isolated sMHCII antigens from the serum of human serum albumin (HSA) -tolerant mice as a single highly glycosylated protein of ~ 60,000 molecular weight, specifically interacting with anti-class II antibodies in Western blotting and ELISA. Mass spectroscopy showed that these sMHCII proteins were loaded with the tolerogenic peptide as well as multiple self peptides. At the cellular level, sMHCII suppressed antigen-specific, and to a lesser degree antigen-non-specific, spleen cell proliferation and induced CD25 in naive T cells. In T cells activated by antigen-seeded macrophages, sMHCII decreased CD28 and increased CTLA-4 protein expression, while decreasing interleukin-2 and increasing interleukin-10 production. In this case, sMHCII proteins were shown to decrease ZAP-70 and LAT phosphorylation. The results presented here for the first time provide evidence for the role of sMHCII proteins in immune response suppression and maintenance of tolerance, revealing novel regulatory mechanisms for immune system manipulation.

T Cells Survey the Stability of the Self: A Testable Hypothesis on the Homeostatic Role of TCR-MHC Interactions

In the lifetime of an individual, every single gene will have undergone mutation on about 10(10) separate occasions. Nevertheless, cancer occurs mainly with advancing age. Here, we hypothesize that the evolutionary pressure driving the creation of the T cell receptor (TCR) repertoire was primarily the homeostatic surveillance of the genome. The subtly variable T cells may in fact constitute an evolutionary link between the invariable innate and hypervariable B cell systems. The new model is based on the homeostatic role of T cells, suggesting that molecular complementarity between the positively selected TCR and the self peptide-presenting major histocompatibility complex molecules establishes and regulates homeostasis, strictly limiting variations of its components. Notwithstanding, the 'homeostatic role of T cells' model offers a more realistic explanation as to how a naïve clonal immune system can cope with the much faster replicating pathogens, despite a limited repertoire that is capable of facing only a small fraction of the vast antigenic universe at a time.

Soluble human leukocyte antigen: A diagnostic indicator of rheumatoid arthritis?

Early stage rheumatoid arthritis (RA) is often difficult to diagnose because initial symptoms are non-specific. To aid diagnosis, suitable serological diagnostic markers are sought. Elevated levels of soluble MHC class II (soluble human leukocyte antigen; sHLA-DR) in human serum have been associated with rheumatoid and 'rheumatoid-like' autoimmune diseases. As a result, sHLA-DR has been suggested as a specific marker of RA. However, reported levels of sHLA-DR in sera of healthy donors vary significantly and the mechanism of release of HLA-DR into serum is poorly understood. Investigations into the diagnostic potential of this molecule necessitate the development of a sensitive and specific sHLA-DR assay. We have investigated multiple ELISA setups to develop such an assay and false positive signal has been carefully removed using a combination of isotype-matched controls and immuno-depletion. sHLA-DR levels in sera of RA patients were not significantly different from those in healthy donors which suggests sHLA-DR has limited utility in the diagnosis of RA. In RA patients, we detected high levels of sHLA-DR in aspirated synovial fluid (SF), but this did not correlate with sHLA-DR levels in serum.

Soluble HLA class I and HLA-DR plasma levels in patients with anterior uveitis

Anterior uveitis (AU) is an autoimmune disease frequently associated with HLA-B27 antigen. Because of the immune regulatory properties of soluble human leukocyte antigen (sHLA) molecules, we quantified sHLA class I (sHLA-I) and sHLA-DR plasma levels in HLA-typed AU patients (n = 60). Randomly selected healthy individuals (n = 128) and HLA-B27 antigen-positive individuals (n = 24) with HLA phenotype frequencies similar to the HLA-B27 antigen-positive AU patients served as control panels. As expected, HLA-B27 phenotype was significantly increased in AU patients (n = 60), compared to healthy controls. Mean sHLA-I levels in AU patients were slightly higher than in randomly selected healthy controls. Regarding AU subgroups, elevated sHLA-I levels were only found in HLA-B27 antigen-negative patients. Compared to controls, sHLA-DR levels were significantly increased in AU patients and the subgroups of HLA-B27 antigen-negative and -positive patients but not Fuchs' heterochromic cyclitis (FHC). AU patients negative for HLA-B27 antigen with a chronic course had higher sHLA-DR levels than those with an acute course. The presence of associated systemic diseases in AU patients was related to elevated sHLA-DR levels. Secretion of sHLA-DR in blood differs among the various forms of AU. Systemic immune activation was present in AU but not in FHC.

HLA-DR regulation and the influence of GM-CSF on transcription, surface expression and shedding

Low surface HLA-DR expression is a feature in sepsis. However, the mechanisms that regulate HLA-DR expression have not been elucidated. The current study investigates regulation of HLA-DR gene transcription, post transcriptional events and shedding of surface HLA-DR, as well as the regulation of HLA-DR by GM-CSF and an immunomodulatory cytokine. Plasma and PBMC were collected from septic patients and healthy volunteers. An ELISA was developed to measure soluble HLA. PCR techniques were used to determine HLA-DR mRNA levels, and flow cytometry and fluorescent microscopy were used for measurement of surface expressed and intracellular HLA-DR. Septic patients fulfilling the criteria of the American College of Chest Physicians (ACCP) for sepsis were recruited for the study (n=70). HLA-DR was measured on three consecutive days, days seven and fourteen. Patients were excluded from the study if on immunosuppressive therapy. Results: Higher levels of shed HLA-DR were found in the plasma of septic patients compared to healthy controls. The level of HLA-DR mRNA was significantly lower in septic patients compared to healthy controls, however an increased intracellular HLA-DR expression was observed. When HL-60 cells were treated with GM-CSF, gene transcription, surface expression and shedding of HLA-DR were all up-regulated. These results indicate that the mechanisms involved in the regulation of HLA-DR in sepsis include shedding of HLA-DR from the cell surface and regulation of HLA-DR gene transcription. Post-translational processing of HLA-DR was also seen to be compromised. GM-CSF was shown to regulate HLA-DR at all these levels.

Soluble HLA-DR and soluble CD95 ligand levels in pregnant women with antiphospholipid syndromes

Antiphospholipid syndrome (APS) is a severe complication in pregnancy that can lead to fetal death in the second or third trimester. As soluble HLA-DR (sHLA-DR) molecules are reported to be implicated in the etiology of pregnancy disorders and of autoimmune diseases, we studied sHLA-DR plasma levels in pregnant women with APS (n = 14) and in women with normal pregnancy (n = 15), in women with high-risk pregnancies such as preeclampsia (PE; n = 20) and intrauterine growth retardation (IUGR; n = 10) and in fertile non-pregnant women (n = 29). The sHLA-DR levels of pregnant women were assessed during the third trimester, at labor, in the first week, and in the third month of puerperium. The results obtained were compared with soluble CD95 ligand (sCD95L), an important signal molecule in the apoptosis pathway. The sHLA-DR levels in pregnant women with APS were approximately three times higher (mean 1.48 +/- 0.15 microg/ml) during the whole observation period than in fertile non-pregnant women (0.54 +/-.06 microg/ml) and nearly double in women with high risk (PE, 0.91 +/- 14 microg/ml; IUGR, 0.94 +/-.21 microg/ml) and in normal pregnancies (0.74 +/- 0.13 microg/ml). Furthermore, sHLA-DR levels of pregnant women with APS were positively correlated with the serum concentration of anti-anticardiolipin immunoglobulin G antibodies. For sCD95L plasma levels, no substantial variations were found among the different groups above. In pregnant women with APS, however, sHLA-DR levels were positively correlated with sCD95L levels. Further studies should clarify the functional involvement of sHLA-DR molecules in the induction of CD95/CD95L-mediated apoptosis pathway that may play a crucial role in the pathology of pregnancies complicated by APS.

Umbilical cord blood dendritic cells are a rich source of soluble HLA-DR: synergistic effect of exosomes and dendritic cells on autologous or allogeneic T-Cell proliferation

In this study, we compared soluble HLA-DR (sHLA-DR) production in the culture supernatants of various cell sources [T and B cells, monocytes and dendritic cells (DCs) either from adult peripheral blood (PB) or umbilical cord blood (UCB)]. DCs produced the highest amount of sHLA-DR molecules as compared to other cell sources, with UCB DCs producing the highest amount. Different kinetics of sHLA-DR production were found between immature and mature UCB DCs (mDC, iDC) (derived either from CD34(+) or CD14(+) cells). Maximum production of sHLA-DR was observed in 72-hour culture supernatants of both CD34- and CD14-derived mDCs, whereas it peaked in the 24-hour culture supernatants from iDC. sHLA-DR molecules were pelleted after sequential centrifugation from UCB CD34(+) DCs and were found to contain both 36 kD alpha-chain and 29 kD beta-chain of HLA-DR, CD86, and Fas molecules. These sHLA-DR containing vesicles/exosomes alone evoked weak proliferative responses from autologous and allogeneic T cells, but the immune response was significantly increased when vesicles/exosomes were presented with DCs.

Soluble HLA-DR levels in serum are associated with therapy and genetic factors in rheumatoid arthritis

As rheumatoid arthritis (RA) is an HLA-DR associated autoimmune disease and soluble HLA-DR (sHLA-DR) molecules have the capacity to regulate the immune response, we studied the sHLA-DR levels in RA patients in view of therapy modalities and clinical and biologic parameters of disease activity. For this sHLA-DR concentrations from 87 RA patients were determined by a sensitive enzyme-linked immunoabsorbent assay (ELISA) format. There was a weak but significant correlation between sHLA-DR levels and disease activity (r 0.186 to 0.287, p < 0.004 to < 0.001). The mean serum sHLA were not significantly different between groups with or without corticosteroids, or undergoing therapy with different disease modifying antirheumatic drugs. However, patients treated with a combination of methotrexate and prednisolone have lower sHLA-DR (206 +/- 21 ng/ml, n = 34) compared with the mean value for all other samples (306 +/- 16, n = 217, p < 0.001). This corresponded with significantly lower EULAR pain and swelling scores, ESR and rheumatoid factor (RF) by latex fixation (p < 0.02 to 0.001) in the former, compared with the latter group. Furthermore, sHLA-DR was, respectively, 267 +/- 15 ng/ml (n = 182) in samples from patients treated with nonsteroidal anti-inflammatory drugs (NSAIDs), and 358 +/- 31 (n = 72) without NSAIDs (p < 0.01). Lower sHLA-DR with NSAIDs contrasted with significantly higher scores for pain, swelling, CRP, and RF by latex fixation and by Waaler-Rose test (p < 0.05 to 0.001). Comparison of subgroups with or without the shared epitope of RA disease (Q)R/KRAA within the HLA-DR beta1-chain confirmed significantly higher parameters of disease activity and sHLA-DR in the presence of this disease associated epitope in our patients. Different mechanisms appear to be involved in sHLA-DR production or release, as their level correlates positively with disease activity under combined therapy with corticosteroids and methotrexate, but decreases with higher disease activity in patients treated with NSAIDs.

Soluble HLA-DR is a potent predictive indicator of disease progression in serum from early-stage melanoma patients

Despite numerous therapeutic options, the prognosis of malignant melanoma, once metastasized, is still poor. Thus, the search for reliable methods to identify patients with high risk of disease progression as early as possible is of major importance. In our study, we analyzed the predictive value of soluble HLA-DR (sHLA-DR) in comparison to S100-beta in serum from 183 melanoma patients of different stages of disease and with or without current therapy using immunosorbent assays. sHLA-DR serum levels of 121 healthy individuals served as controls. We found significantly (p < 0.0005) reduced sHLA-DR serum levels in melanoma patients (0.70 +/- 0.08 SEM microg/ml) compared to controls (1.49 +/- 0.10 SEM microg/ml). Reduced sHLA-DR and increased S100-beta levels were associated with advanced disease stages and tumor load. S100-beta was increased under cytostatic therapy (p < 0.0005), whereas sHLA-DR was not influenced by therapy modalities. Univariate analysis showed an association of sHLA-DR < 0.3 microg/ml and S100-beta > 0.12 microg/l with poor overall (p = 0.021 and p = 0.0009) and progression-free survival (p < 0.0005 and p = 0.0025). Multivariate analysis revealed disease stage (p = 0.0093) and tumor burden (p < 0.0005) as independent predictive factors for overall survival, and sHLA-DR (p = 0.0007) and tumor burden (p = 0.0015) for progression-free survival. In contrast to S100-beta, sHLA-DR serum concentrations < 0.3 microg/ml were strongly associated (p = 0.0001) with poor progression-free survival in a subgroup of 60 nonmetastasized patients. In conclusion, our results suggest sHLA-DR as a potent prognostic serum marker in melanoma patients superior to S100-beta in helping to identify early-stage patients at high risk of disease progression.

Genetics of rheumatoid arthritis: is there a scientific explanation for the human leukocyte antigen association?

Human leukocyte antigen genes associated with rheumatoid arthritis are commonly found in the unaffected population, implying that causal mechanisms of disease involve interactions between these genes and other factors. A variety of approaches-genetic, structural, and immunologic-are used to explore possible molecular interactions that may contribute to understanding the basis for this disease association. The specific relation between human leukocyte antigen-DR4 alleles and rheumatoid arthritis remains one of the strongest and most thoroughly studied examples of human leukocyte antigen risk genes among human autoimmune disorders.

The shared epitope and severity of rheumatoid arthritis

After two decades of research involving thousands of RA patients, it is still not possible to precisely define the relation of HLA-DRB1 SE alleles to RA severity. Improvements in our understanding require more careful consideration of several factors such as ethnicity, gender, and the specific SE allele and genotype inherited. Large studies of heterogeneous groups of patients are required and indicate the need for collaborative efforts among researchers. In the interim, meta-analysis of the existing literature may provide some insight, because it allows utilization of the tremendous amount of research already completed. A preliminary meta-analysis highlighted the significant heterogeneity among the existing literature, and a more ambitious meta-analysis that uses individual patient-level data is currently ongoing. Profound implications exist for determination of the precise relationship between the SE and RA severity. This information could be valuable in identifying patients at greater risk of severe complications or as a stratification variable for clinical trials. Moreover, patients genetically predisposed to severe disease may benefit from early initiation of more aggressive therapy. Ultimately, clarification of the role of the SE may be valuable for the development of specific therapies directed toward DRB1 and related targets.

Actions of human interleukin-4/B-cell stimulatory factor-1 on proliferation and differentiation of enriched hematopoietic progenitor cells in culture

We studied the effects of recombinant human interleukin-4 (IL-4) on colony formation by enriched hematopoietic progenitors. IL-4 alone did not support colony formation at all. When IL-4 was combined with granulocyte colony-stimulating factor (G-CSF), the number of pure neutrophil colonies increased three times over that supported by G-CSF alone. IL-4 added 5 days after the addition of G-CSF failed to exert this synergistic effect, indicating that IL-4 acts on the early stage of proliferation. The mapping experiments (sequential observation of colony formation) have clearly shown that IL-4 did not initiate progenitor cell proliferation. Based on these data, IL-4 may possess a direct action on progenitor cells; however, it can only act as a costimulant with G-CSF. In contrast, IL-4 had possible inhibitory effects on macrophage colony formation supported by interleukin-3 (IL-3) and macrophage colony-stimulating factor (M-CSF). In other words, IL-4 may induce progenitor cells to become sensitive to G-CSF and thereby induce neutrophil differentiation. Delayed addition experiments demonstrated that human IL-4, unlike murine IL-4, could support neither proliferation nor survival of erythroid burst or mixed colony forming cells. Neutrophil colony forming cells only survived and recovered after addition of G-CSF and erythropoietin on day 5 of incubation. On the other hand, IL-3 supported neutrophil, erythroid burst, and mixed colony forming cells as reported previously (Sonoda et al, Proc Natl Acad Sci USA, 85:4360, 1988). These results led us to propose that IL-4 possibly acts with more mature progenitor cells than those of IL-3 or granulocyte-macrophage (GM)-CSF.