Increased level of serum HLA class I antigens in patients with systemic lupus in patients with systemic lupus erythematosus. Correlation with disease activity

Open MHC Class I Conformers: A Look through the Looking Glass

Studies carried out during the last few decades have consistently shown that cell surface MHC class I (MHC-I) molecules are endowed with functions unrelated with antigen presentation. These include cis–trans-interactions with inhibitory and activating KIR and LILR, and cis-interactions with receptors for hormones, growth factors, cytokines, and neurotransmitters. The mounting body of evidence indicates that these non-immunological MHC-I functions impact clinical and biomedical settings, including autoimmune responses, tumor escape, transplantation, and neuronal development. Notably, most of these functions appear to rely on the presence in hematopoietic and non-hematopoietic cells of heavy chains not associated with β2m and the peptide at the plasma membrane; these are known as open MHC-I conformers. Nowadays, open conformers are viewed as functional cis-trans structures capable of establishing physical associations with themselves, with other surface receptors, and being shed into the extracellular milieu. We review past and recent developments, strengthening the view that open conformers are multifunctional structures capable of fine-tuning cell signaling, growth, differentiation, and cell communication.

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.

Serum antibodies to human leucocyte antigen (HLA)-E, HLA-F and HLA-G in patients with systemic lupus erythematosus (SLE) during disease flares: Clinical relevance of HLA-F autoantibodies

T lymphocyte hyperactivity and progressive inflammation in systemic lupus erythematosus (SLE) patients results in over-expression of human leucocyte antigen (HLA)-Ib on the surface of lymphocytes. These are shed into the circulation upon inflammation, and may augment production of antibodies promoting pathogenicity of the disease. The objective was to evaluate the association of HLA-Ib (HLA-E, HLA-F and HLA-G) antibodies to the disease activity of SLE. The immunoglobulin (Ig)G/IgM reactivity to HLA-Ib and β2m in the sera of 69 German, 29 Mexican female SLE patients and 17 German female controls was measured by multiplex Luminex(®)-based flow cytometry. The values were expressed as mean flourescence intensity (MFI). Only the German SLE cohort was analysed in relation to the clinical disease activity. In the controls, anti-HLA-G IgG predominated over other HLA-Ib antibodies, whereas SLE patients had a preponderance of anti-HLA-F IgG over the other HLA-Ib antibodies. The disease activity index, Systemic Lupus Erythematosus Disease Activity Index (SLEDAI)-2000, was reflected only in the levels of anti-HLA-F IgG. Anti-HLA-F IgG with MFI level of 500-1999 was associated with active SLE, whereas inactive SLE revealed higher MFI (>2000). When anti-HLA-F IgG were cross-reactive with other HLA-Ib alleles, their reactivity was reflected in the levels of anti-HLA-E and -G IgG. The prevalence of HLA-F-monospecific antibodies in SLE patients was also associated with the clinical disease activity. Anti-HLA-F IgG is possibly involved in the clearance of HLA-F shed from lymphocytes and inflamed tissues to lessen the disease's severity, and thus emerges as a beneficial immune biomarker. Therefore, anti-HLA-Ib IgG should be considered as a biomarker in standard SLE diagnostics.

Bio-modulators in platelet-rich plasma: a comparison of the amounts in products from healthy donors and patients produced with three different techniques

BACKGROUND

Platelet-rich plasma consists of platelets concentrated in a small volume of plasma and constitutes a reservoir of bio-modulators potentially useful in tissue repair. The amounts of bio-modulators detectable in platelet-rich plasma prepared with various commercial or "in house" methods have been reported, but virtually all the analyses described have been performed on platelet-rich plasma derived from healthy donors. Since leucocyte contamination is technically unavoidable, we investigated whether platelet-rich plasma prepared from patients could contain different amounts of bio-modulators because of a possible activated status of the leucocytes.

MATERIALS AND METHODS

We evaluated platelet-rich plasma prepared with three different techniques (the commercial Vivostat and Biomet recover GPS II systems and an "in house" method) starting from whole blood from healthy donors and patients. Specifically, we compared the levels of sHLA-I, sFasL, platelet-derived growth factor, transforming growth factors-beta and vascular endothelial growth factor in the platelet-rich plasma releasates according to the method of preparation and to the immune system activation status of the subjects.

RESULTS

With the exception of sHLA-I levels, no differences were found in the surrogate indices of lymphocyte activation between healthy donors and patients. No significant differences were found in sHLA-I, sFasL, platelet-derived growth factor, transforming growth factors-beta and vascular endothelial growth factor levels detectable in platelet-rich plasma produced with the three different methods in either healthy donors or patients.

DISCUSSION

On the whole our findings indicate that the overall content of bio-modulators in autologous platelet-rich plasma is not influenced by T-lymphocyte activation status, at least in patients with uncomplicated femoral fractures. The amounts of sFasL and sHLA-I detected in all the platelet-rich plasma releasates studied were very small, far below the amounts detectable in all clinically available blood derivatives and absolutely insufficient to induce sHLA-I and/or sFasL mediated immunomodulation.

The β2-microglobulin-free heterodimerization of rhesus monkey MHC class I A with its normally spliced variant reduces the ubiquitin-dependent degradation of MHC class I A

The MHC class I (MHC I) molecules play a pivotal role in the regulation of immune responses by presenting antigenic peptides to CTLs and by regulating cytolytic activities of NK cells. In this article, we show that MHC I A in rhesus macaques can be alternatively spliced, generating a novel MHC I A isoform (termed "MHC I A-sv1") devoid of α(3) domain. Despite the absence of β2-microglobulin (β2m), the MHC I A-sv1 proteins reached the cell surface of K562-transfected cells as endoglycosidase H-sensitive glycoproteins that could form disulfide-bonded homodimers. Cycloheximide-based protein chase experiments showed that the MHC I A-sv1 proteins were more stable than the full-length MHC I A in transiently or stably transfected cell lines. Of particular interest, our studies demonstrated that MHC I A-sv1 could form β2m-free heterodimers with its full-length protein in mammalian cells. The formation of heterodimers was accompanied by a reduction in full-length MHC I A ubiquitination and consequent stabilization of the protein. Taken together, these results demonstrated that MHC I A-sv1 and MHC I A can form a novel heterodimeric complex as a result of the displacement of β2m and illustrated the relevance of regulated MHC I A protein degradation in the β2m-free heterodimerization-dependent control, which may have some implications for the MHC I A splice variant in the fine tuning of classical MHC I A/TCR and MHC I A/killer cell Ig-like receptor interactions.

Soluble MHC I and soluble MIC molecules: potential therapeutic targets for cancer

It has become clear that soluble MHC I (sMHC I) and soluble MIC (sMIC), which are highly elevated in sera of cancer patients, can be viewed to be tolerogenic, and that metalloproteinases are involved in their generation process. In this review, an overview is provided of the recent progress made in the sMHC I and sMIC fields, with emphasis on their structure, formation, and function, and the key-questions that still await answers are addressed. Understanding better their formation mechanism, it will become more feasible to modulate the immune responses in cancer patients by targeting molecules involved in their generation process.

Levels of soluble HLA-I and beta2M in patients with acute myeloid leukemia and advanced myelodysplastic syndrome: association with clinical behavior and outcome of induction therapy

beta-2 Microglobulin (beta2M), a subunit of human leukocyte antigen-class I (HLA-I), is well established as a marker of prognosis in various solid tumors and hematologic malignancies. The prognostic role of intact free-circulating HLA-I (sHLA-I) is less well understood. We compared the clinical relevance of plasma levels of sHLA-I and beta2M in patients with acute myeloid leukemia (AML; n=209) or advanced myelodysplastic syndrome (MDS; n=98). sHLA-1 and beta2M levels were significantly higher in AML and MDS patients than in control subjects, but did not differ significantly between the two disease groups. In AML patients, multivariate analysis showed both sHLA-1 and beta2-M to be highly predictive of complete remission (CR), survival and duration of complete response (CRD). In MDS, the predictive value of the two markers differed substantially from one another: beta2M was associated with survival, CR and CRD, whereas sHLA-I was not. These findings not only establish the role of sHLA-I as a tumor marker in AML but also support that MDS is clinically and biologically distinct from AML. sHLA-I has been reported to be an immunomodulator inhibiting the cytotoxic effects of T-lymphocytes, which may offset its predictive value for disease aggressiveness in patients with MDS.

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.

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.

Size variants of beta-2-microglobulin-free human leucocyte antigen class I heavy chain make different contributions to its serum increase in multiple myeloma

We previously showed that serum beta-2-microglobulin (beta2m)-free human leucocyte antigen (HLA) class I heavy chain (FHC) levels were increased in MM and correlate with disease activity. The present investigation, carried out in 124 multiple myeloma patients, studied the expression of the three size variants of FHC, namely the 42 kDa intact heavy chain (A variant, AV), released through a shedding process, and the truncated FHC (tFHC) 39 kDa (BV) and 36-35 kDa (CV) released by means of membrane-type metalloprotease activity. The increase in FHC correlated with a high expression percentage of BV (r = 0.32, P = 0.0002) and tFHC (r = 0.42, P < 0.0001), which could help to discriminate multiple myeloma from monoclonal gammopathy of undetermined significance (tFHC mean ratio = 3.2; Mann-Whitney U-test, P < 0.0001). tFHC levels highly correlated with other disease activity markers, namely haemoglobin (r = -0.35; Spearman's rank, P = 0.0001), percentage of bone marrow plasma cells (r = 0.4, P < 0.0001) and beta2m levels (r = 0.36, P < 0.0001), while only the last barely correlated (r = 0.2, P = 0.03) with AV. Finally, the 0.4, 0.57 and 0.71 mg/l BV, tFHC and (to a lesser extent) FHC cut-off values divided patients into two groups with different survival curves (P = 0.0005, P = 0.0025 and P = 0.04 respectively). These data are in favour of a correlation between disease aggressiveness and cleavage of these variants by membrane-type metalloprotease enzymes.

Soluble HLA class I induces NK cell apoptosis upon the engagement of killer-activating HLA class I receptors through FasL-Fas interaction

The engagement of the activating isoforms of C-type lectin inhibitory receptor (CLIR) or killer Ig-like receptor (KIR) by their natural ligands, represented by soluble HLA-I (sHLA-I) molecules, induced programmed cell death of natural killer (NK) cells. Indeed, NK cell apoptosis elicited by either putative HLA-E and HLA-F (sHLA-I non-A, -B, -C, and -G) or sHLA-I-Cw4 or -Cw3 from untransfected or -Cw4 or -Cw3 alleles transfected HLA-A(-), B(-), C(-), G(-), E(+), F(+) 721.221 lymphoblastoid cell line, respectively, was blocked by covering the corresponding activating receptor with either anti-CLIR- or anti-KIR-specific monoclonal antibodies (mAbs). After sHLA-I-activating receptor interaction, NK cells produced and released Fas ligand (FasL), which in turn led to NK cell apoptosis by interacting with Fas at the NK cell surface. Blocking anti-Fas mAb, or anti-FasL mAb, inhibited sHLA-I-mediated apoptosis via activating receptor in NK cell clones. This apoptosis was inhibited by NK cell treatment with cyclosporin A, whereas this drug had no effect on activating receptor-mediated activation of cytolysis. Conversely, concanamycin A, an inhibitor of vacuolar type H(+)-adenosine triphosphatase (H(+)-ATPase) of granules, inhibited activating receptor-induced NK cell cytolysis, suggesting that activating receptor-mediated apoptosis and cytolysis can use different intracellular pathways. Furthermore, a large amount of interferon-gamma (IFN-gamma) was detectable in culture supernatant of activating receptor(+) NK cells incubated with the appropriate sHLA-I ligand. Again, cyclosporin A, but not concanamycin A, strongly reduced activating receptor-mediated IFN-gamma production. This suggests that activating receptor-induced apoptosis of NK cells could play a role in eliminating potentially harmful NK cell clones and, at the same time, it leads to production of IFN-gamma, an antiviral cytokine able to amplify immune responses.

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.

Levels of soluble human leukocyte antigen class 1 are increased in Graves' disease and toxic multinodular goiter and correlate with the levels of triiodothyronine

Soluble human leukocyte antigens class 1 (sHLA-1) are postulated to play a role in immunomodulation. Thyroid hormones and thyroid stimulating hormone influence expression of major histocompatibility complex (MHC) class 1 genes. We hypothesized similar changes in sHLA-1 with changes in the thyroid hormone. We measured serum levels of sHLA-1 in 140 normal controls, 11 patients with toxic multinodular goiter and 26 patients with active Graves' disease. On follow-up 1 year after treatment for Graves' disease, we repeated the measurement of the levels of sHLA-1 in 21 patients. Levels of sHLA-1 were markedly elevated in the group of patients with active Graves' disease compared to the normal controls (p = 0.00016). The levels of sHLA-1 were also elevated significantly in patients with toxic multinodular goiter compared to normal controls (p = 0.034). There is no significant difference between genders and the two races tested among patients with Graves' disease in contrast to controls. Free triiodothyronine (T(3)) levels positively correlated with the levels of sHLA-1 (r = 0.61). On follow-up after treatment for Graves' disease, levels of sHLA-1 decreased by 62% with p = 0.0006 (active Graves vs. follow-up). We conclude that there is a definite association between thyroid hormones and sHLA-1 levels.

Soluble HLA class I molecules induce natural killer cell apoptosis through the engagement of CD8: evidence for a negative regulation exerted by members of the inhibitory receptor superfamily

Herein, we show that CD8(dull), CD8(intermediate), and CD8(bright) natural killer (NK) cell clones can be identified. Triggering of CD8 with its natural ligand(s), represented by soluble HLA class I (sHLA-I), isolated either from serum of healthy donors or from HLA-I(-) 721.221 lymphoblastoid cell line transfected with HLA-A2, -Cw4, and -Bw46 alleles, or HLA-G1 leads to NK cell apoptosis. The magnitude of this effect directly correlated with the level of CD8 expression. sHLA-I-induced apoptosis depends on the interaction with CD8, as it was inhibited by masking this molecule with specific monoclonal antibodies (mAbs). Moreover, sHLA-I or CD8 cross-linking with specific mAbs elicited intracellular calcium increases, Fas ligand (FasL) messenger RNA transcription, and FasL secretion, which were needed for delivering the death signal. Indeed, this apoptosis was inhibited by preincubation of NK cell clones with Fas or FasL antagonist mAbs, indicating that the Fas/FasL pathway is involved. Furthermore, members of the inhibitory receptor superfamily, such as CD94/NKG2 complex or killer inhibitory receptors, were shown to exert an inhibitory effect on sHLA-I-mediated apoptosis and secretion of FasL. These findings suggest that interaction between sHLA-I and CD8 evokes an apoptotic signal that is down-regulated by inhibitory receptor superfamily that function as survival receptors in NK cells.

Transmodulation of cell surface regulatory molecules via ectodomain shedding

Cell responses to exogenous stimuli often result in a rapid decrease of cell surface density of a wide range of diverse regulatory proteins, receptor and adhesion molecules in particular. This decrease may occur in a ligand-dependent fashion (down-regulation), following endocytosis and degradation by lysosomal proteases, or by down-modulation, where molecules are targeted by endoproteases directly on cell surface. These proteases are recruited by trans-modulating agents, different from ligand, which act via their own receptors and the related intracellularly-generated signals. Endoproteolytic activity determines the release of large portions (shedding) of substrate proteins, called ectodomains, which are usually not ligand-bound, and therefore represent biologically-active molecules. Ectodomain shedding is involved in a number of pathophysiological processes, such as inflammation, cell degeneration and apoptosis, and oncogenesis. Common features of the process, such as the involvement of protein kinase C and of transmembrane metalloproteases, have been identified. In this review, we summarize basic concepts on down-modulation and ectodomain shedding, and provide an update of the issue with respect to: (i) new entries to the list of molecules found involved in the process; (ii) current views about the upstream control of shedding, i.e. the pathways linking the signals triggered by the trans-modulating agents to the activation of endoproteolytic activity on the cell surface.

Increased level of soluble HLA class I antigens in systemic lupus erythematosus: correlation with anti-DNA antibodies and leukopenia

The concentration of soluble HLA class I (sHLA-I) was measured by ELISA in serum samples from 30 well-characterised SLE patients at high and low disease activity states and from 100 healthy controls. HLA-A allotypes in the patients were analysed by a PCR-based typing technique. A higher level of sHLA-I was found in SLE patient sera both at high and low disease activity than in controls (P< 0.001). The sHLA-I level was further increased during active disease (P< 0.01). Concentrations of sHLA-I correlated with anti-dsDNA antibodies at high disease activity, but not with disease activity as analysed by a modified SLEDAI. Numbers of leukocytes and lymphocytes, as well as levels of C1q and C3 correlated inversely with sHLA-I concentration. In five serial samples from ten patients the sHLA-I level co-varied with disease activity. Presence of HLA allotype A9 was associated with higher sHLA-I levels in both patients (P< 0.001) and controls (P< 0.001). We conclude that the increased sHLA-I concentration in SLE patients was related to several laboratory parameters reflecting disease activity suggesting that sHLA-I molecules are connected with the disease process. Increased sHLA-I level due to HLA-A allotype was not a disease susceptibility factor for SLE.

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

We investigated correlations between soluble HLA-DR (sHLA-DR) molecules and several clinical, biological and genetic parameters associated with rheumatoid arthritis (RA) disease activity. Serum sHLA-DR concentrations were determined in 146 samples from 89 RA patients by an ELISA format, using an antibody combination of mouse and rat monoclonal anti-human HLA-DR antibodies. The mean sHLA-DR serum level in RA patients was significantly increased with 277+/-19 ng/ml compared to 142+/-13 ng/ml of 80 healthy controls (P<0.001). In ascending order of significance, correlations were found between serum sHLA-DR and EULAR swelling and pain scores, Waaler-Rose, RA factor, ESR and CRP (P=0.025 to P<0.001). High sHLA-DR levels were defined above 374 ng/ml that was the 95% confidence interval of the controls. Thirty-seven blood samples (25%) in 31 RA patients were above this level. The EULAR pain and swelling scores, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) and RA factor were higher (P=0.044 to P<0.001) at the moment of high sHLA-DR concentrations, compared to the lower concentrations. Higher disease activity was further found in groups of RA patients respectively heterozygous or homozygous for the disease-associated epitope (Q)R/KRAA within the HLA-DRB1 chain, compared to the group without this epitope (P<0.017 for part of the results). Likewise, sHLA-DR was respectively 169+/-17 (no disease associated epitope), 324+/-34 (heterozygous) and 442+/-69 ng/ml (homozygous for the disease-associated epitope on HLA-DRB1 alleles) (P<0.017). In conclusion, this study shows significant correlations between serum sHLA-DR levels and RA disease activity parameters, as well as increased sHLA-DR in patients with disease-associated epitope on HLA-DRB1 alleles.

Toxic effects of SLE serum on normal monocytes in vitro: cell death induced by apoptosis related to complement dysfunction

The aim of this study was to assess toxic effects of systemic lupus erythematosus (SLE) serum on blood peripheral mononuclear cells from healthy donors and to evaluate if complement activation was involved. Monocytes from a healthy donor were incubated with 20 sera from ten SLE patients in both high and low disease activity states. After incubation non-adherent cells were analysed by flow cytometry. Serum from six SLE patients induced an increased cell death, four in active disease only, one in the inactive state and one in the active and the inactive state. Five of these sera, three with high and two with low disease activity, induced an increased apoptosis in the monocytes. Proportion of apoptotic cells correlated inversely with C1q and C3 concentration in the active disease sera, but not with disease activity as evaluated by SLEDAI. Apoptosis could be induced by addition of active C1s or antigen/antibody complexes to normal serum before incubation. Serum with complexes added induced increased tumour necrosis factor-alpha secretion from mononuclear cells, but SLE patient sera did not. The results demonstrate that the toxic effect of serum from SLE patients on healthy monocytes is explained by induction of apoptosis. The induction process is suggested to be connected with complement activation in the serum.

Increased beta2-microglobulin-free HLA class I heavy chain serum levels in the course of immune responses to viral antigens and to mismatched HLA antigens

Besides being present in serum in association with beta2-mu, HLA class I heavy chains are also present in serum as beta2-micro-free moieties. The increase in serum levels of beta2-micro-associated HLA class I heavy chains in conditions associated with an activation of the immune system have prompted us to measure the serum levels of beta2-mu-free HLA class I heavy chains in the course of immune responses to viral antigens and to mismatched histocompatibility antigens. The serum level of beta2-mu-free HLA class I heavy chains, like that of beta2-mu-associated HLA class I heavy chains was significantly increased in patients affected by advanced HIV-1 infection or by chronic hepatitis C (CHC). In the latter group of patients an association was found between a reduction in the beta2-mu-free HLA class I heavy chain serum level and response to therapy with interferon alpha and ribavirin. Moreover, the beta2-mu-free HLA class I heavy chain serum level was increased more than that of beta2-mu-associated HLA class I heavy chains during episodes of liver ischemia following liver transplantation and in the course of acute graft rejection and of acute graft-versus-host-disease (GVHD) after allogeneic bone marrow transplantation (BMT). These results suggest that the serum levels of beta2-mu-free and beta2-mu-associated HLA class I heavy chains are independently regulated. Furthermore, beta2-mu-free HLA class I heavy chain serum level may be a useful marker to monitor response to therapy in CHC patients and the clinical course of liver and bone marrow grafts.

Increased serum concentrations of soluble HLA-class I antigens in hepatitis C virus related mixed cryoglobulinaemia

OBJECTIVE

To investigate whether quantitative alterations of both beta(2)microglobulin (beta(2)micro) associated HLA class I heavy chains (sHLA-I) and beta(2) micro free class I heavy chains (sHLA-FHC) in sera of patients with hepatitis C virus (HCV) infection occur and whether they distinguish patients with mixed cryoglobulinaemia (MC).

METHODS

83 HCV infected patients were studied and divided into three groups: (A) without cryoglobulinaemia (n=21), (B) with polyclonal MC (n=20), (C) with monoclonal MC (n=42). Serum sHLA-I and sHLA-FHC were measured by double determinant radioimmunoassay using monoclonal antibodies: TP25.99 as catching antibody, and NAMB-1 and HC-10 as revealing antibodies. Western blot identified HLA-I isoforms.

RESULTS

The serum concentrations of sHLA-I and of sHLA-FHC in HCV infected patients versus controls were respectively 1.3(0.5) microg/ml (mean (SD)) versus 0.8 (0.3) (p<0. 001) and 13.9 (7.1) ng/ml versus 9.2 (5) (p<0.001). sHLA-I were 1.01 (0.4) microg/ml in group A, 1.04 (0.4) microg/ml in group B, and 1. 47 (0.4) microg/ml in group C (p=0.001). Statistical analysis showed a significant difference versus controls for groups B (p<0.02) and C (p<0.001). sHLA-FHC were 12.8 (8.3) ng/ml in group A, 17.2 (7.1) ng/ml in group B, and 12.9 (6.2) ng/ml in group C (p<0.02). A significant difference versus controls for each group was found (p<0. 02, p<0.001, and p<0.02, respectively). Different patterns of sHLA-I isoforms were observed.

CONCLUSIONS

Increased serum concentrations of sHLA-I and sHLA-FHC characterise HCV infected patients. The highest sHLA-I concentrations seem to distinguish patients with monoclonal MC. In this last condition sHLA could play a part in the HCV escape and in B cell proliferation. The significance of sHLA-FHC is still undefined.

Serum levels of beta-2-microglobulin-free heavy chain of HLA class I antigen in healthy individuals: relationship to their class I allotype

An ELISA-based double determinant immunoassay has been established to measure the soluble beta2-microglobulin (beta2m)-free heavy chain (FHC) of the HLA-B, -C (and HLA-A3, -A28 and -A30) class I molecular complex in sera from 212 HLA-typed healthy unrelated individuals. FHC was calculated by means of a standard curve constructed using serial concentrations of beta2m-associated HLA-class I heavy chain (HLA-I)/FHC purified from cultured human lymphoid cell C1R-sB7-supernatant. The mean FHC concentration (+/-SD) was 0.25 mg/l (+/-0.2). Its median concentration did not statistically differ between males and females, though the male/female ratio was greater in the high secretor (FHC >0.45 mg/l; mean + 1SD) than in the low secretor group (FHC < 0.05 mg/l; mean - 1SD). FHC < 0.05 mg/l was statistically (Fisher's exact test) associated with HLA-B17 (p = 0.003); FHC > 0.45 mg/l was statistically associated with HLA-B35 (p = 0.003) and -Cw4 (p = 0.002). None of these allele-positive groups showed a mean FHC concentration 1.5 times higher than that of the corresponding allele-negative ones. This allotype-dependent HLA-B and C FHC enhancement was less marked than that previously reported for HLA-I in individuals carrying HLA-A9 (and its splits). These results indicate that FHC could be a more valuable marker when its levels are compared among individuals carrying different allotypes. Moreover the lack of correlation between FHC and HLA-I levels measured in 52 HLA-A3, -A28 or -A30 positive individuals suggests that the two molecules may be regulated by different metabolic pathways and their serum expression may have a different biological significance.

Increased serum levels of beta2m-free HLA class I heavy chain in multiple myeloma

Serum levels of beta2-microglobulin (beta2m)-free HLA class I heavy chain (FHC) in 94 patients with multiple myeloma (MM) were higher than in 29 patients with monoclonal gammopathy of undetermined significance (MGUS) (P = 0.023) and in 97 sex- and age-matched healthy controls (P < 0.0001). Spearman correlation analysis indicated that in MM, FHC correlated with beta2m (r = 0.31, P = 0. 003) and the percentage of bone marrow plasma cells (BMPC%) (r = 0. 36, P = 0.002), whereas beta2m, in addition to BMPC% (r = 0.43, P = 0.0003), also correlated with creatinine levels (r = 0.63, P < 0.0001), haemoglobin levels (r = -0.35, P = 0.0007) and patient age (r = 0.34, P < 0.0011). Furthermore, MM patients with poor prognosis (beta2m >/= 6 mg/l) displayed higher FHC levels than those with a better prognosis (beta2m < 6mg/l) (P < 0.021). At variance from beta2m, these levels were not influenced by renal failure, as indicated by the lack of Spearman correlation of FHC with creatinine concentration and of statistical significance between the median FHC concentration of MM patients with creatinine < 176.6 micromol/l and those with creatinine >/= 176.6 micromol/l (P = 0.3). Stratification of patients according to disease activity and stage showed that FHC levels were only statistically different (P = 0.04) for disease activity, whereas beta2m and C-reactive protein were not. Taken together, our data indicate that serum FHC may be a useful disease marker in MM.

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.