Release Of Beta 2-microglobulin Research Articles

Microarray analysis reveals the involvement of beta-2 microglobulin (B2M) in human osteoarthritis

Objective To assess whether beta-2 microglobulin (B2M) has effects on articular chondrocytes that would implicate B2M involvement in osteoarthritis (OA) pathogenesis.MethodsThe mRNA levels of B2M in fetal and osteoarthritic chondrocytes were detected by RT–PCR. B2M levels in synovial fluid and tissue cultured media from cartilage explants were tested using B2M ELISA kit. Primary cultured chondrocytes were used for proliferation and microarray experiments.Results The average B2M level in OA synovial fluid is significantly higher than that found in normal synovial fluid. However, there was no significant difference in B2M synovial fluid levels amongst differing OA stages. The release of B2M by osteoarthritic cartilage was detectable after 24h in culture and continued to increase during the 72h study period. B2M had an inhibitory effect on chondrocyte growth at 1.0μg/ml, and became significantly inhibitory at 10.0μg/ml. Genes regulated by B2M were detected through microarray technology. Twenty genes were found to be up-regulated by B2M, including collagen type III which is known to be up-regulated in OA. Eleven genes were found to be down-regulated at least two-fold by B2M.Conclusion These results indicate that B2M is highly expressed in OA cartilage and synovial fluid compared to normal, and suggest that B2M may have effects on chondrocyte function that could contribute to OA pathogenesis.Copyright 2002 OsteoArthritis Research Society International. Published by Elsevier Science Ltd. All rights reserved.

Effects of alpha-interferon on serum beta-2-microglobulin.

Beta-2-microglobulin (B2M) forms the small invariable light chain subunit of class I HLA antigens on the cell membrane of all nucleated cells. During the continuous turnover of the HLA molecules, B2M is shed from the cell membrane into blood. Lymphocytes are the main source of serum free B2M. Serum B2M concentration is increased in renal diseases, various malignant diseases and some inflammatory and autoimmune disorders. In lymphatic malignancies serum B2M has significant prognostic value. Interferons (IFNs) have the ability to enhance the expression of class I and II histocompatibility antigens. Accordingly, IFNs cause a rise in formation and release of B2M. Currently, treatment with IFN alpha is used in diseases, like multiple myeloma, where serum B2M measurements are used to assess tumor burden. We have measured serum B2M levels during IFN alpha treatment in patients with both multiple myeloma and chronic myeloproliferative diseases, and IFN alpha caused a significant increase in serum B2M. It can be concluded that use of IFN alpha abolishes the value of serum B2M as an indicator of disease activity.

Mixed Enzyme‐Linked Immunosorbent Assay (MELISA) for HLA Class I Antigen: a Plasma Membrane Marker

This study introduces a simple, reproducible assay for HLA class I antigen using antibodies against beta 2-microglobulin and the heavy chain on HLA. The sandwich technique was named mixed enzyme-linked immunosorbent assay (MELISA), and was designed for identification of plasma membranes in neutrophil subcellular fractions. The subcellular localization of HLA was identical to that of other plasma membrane markers, [3H]concanavalin A and detergent-independent alkaline phosphatase, and was unchanged by stimulation of cells by weak and strong secretagogues. In addition to the presence as part of the HLA complex in the plasma membrane uncomplexed beta 2-microglobulin is present in the specific granules of neutrophils. However, the release of beta 2-microglobulin from intact neutrophils stimulated with formyl-methionylleucylphenylalanine was much higher than could be explained by exocytosis of specific granules. Subcellular fractionation studies demonstrated that beta 2-microglobulin is localized in fractions characterized by latent alkaline phosphatase and released from this novel secretory compartment in response to stimulation with formyl-methionylleucylphenylalanine.

Cytokines in the Control of Beta-2 Microglobulin Release. I. In vitro Studies on Various Haemopoietic Cells

The role of cytokines in the control of beta-2 microglobulin release from various haemopoietic cells was studied in vitro. Cell types investigated were resting cells or blasts of the T Cell, B cell or monocyte-macrophage lineage. Mediators used in these experiments were r-IFN-α 2c, r-IFN-γ, r-TNF-α, r-TNF-ß, r-IL 1, r-IL 2 and r-GM-CSF. Nanogram amounts of some of these mediators strongly affected beta-2 microglobulin release in vitro. r-IFN-γ, r-IFN-α 2c and r-IL 2 strongly enhanced and r-TNF-α and r-TNF-ß occasionally increased shedding of beta-2 microglobulin. r-IL 1 and high concentrations of r-IFN-α 2c were inhibitory, whereas r-GM-CSF was ineffective. The impact of antigenic stimulation on beta-2 microglobulin release in mixed lymphocyte culture (MLC) was also studied. Stimulation with alloantigens in MLC greatly enhanced beta-2 microglobulin shedding, and this enhancement could be inhibited by a monoclonal antibody neutralizing human IFN-γ. Among the various cell types studied, macrophages derived from peripheral blood monocytes were most susceptible to cytokine-induced alterations of beta-2 microglobulin shedding. From these data, we conclude that cytokines not only control the static expression of beta-2 microglobulin on the surface of haemopoietic cells but also largely affect their shedding.

Cytokines in the Control of Beta-2 Microglobulin Release. II. In vivo Studies with Recombinant Interferons and Antigens

The influence of in vivo application of recombinant interferon-alpha 2c (IFN-α 2c) and recombinant interferon-gamma (IFN-γ) on beta-2 microglobulin levels was studied in eight patients with chronic myelogenous leukaemia or advanced renal cell carcinoma. Data indicated enhanced beta-2 microglobulin biosynthesis in close temporary association with injection of both types of interferons. The influence of in vivo stimulation by allogenic leukocytes and the influence of renal allografts or cytomegalovirus infection on serum beta-2 microglobulin and IFN-γ levels were also studied. Increased beta-2 microglobulin concentrations were observed again in each of these clinical situations and were closely associated with enhanced endogenous interferon production. From these in vivo data and the in vitro data presented in the preceding publication, (1) we conclude that endogenous interferon levels are crucial for the regulation of beta-2 microglobulin release in vivo.

Removal, generation and adsorption of beta-2-microglobulin during hemofiltration with five different membranes.

Removal of beta 2-microglobulin (B2MG) from uremic plasma during hemofiltration in 5 patients using polysulfone (F60), acrylonitrile (AN69), polyamid (FH77), polyacrylonitrile (PAN200) and cellulose-acetate (Duo-Flux) membranes was investigated. The reduction in plasma concentration of B2MG (corrected for hemoconcentration during treatment) was greatest for the F60 hemofilter (61%, sieving coefficient 0.55 at end of treatment) and the AN69 (48%, sieving coefficient 0.45 at end of treatment, while the PAN200 membrane showed no reduction in plasma concentration of B2MG during treatment. Mass balance for B2MG showed that there was a continued net adsorption of B2MG in the AN69 membrane (about 120 mg) throughout the treatment, while insignificant amount of B2MG was absorbed by the F60 membrane. The results with the PAN200 showed a 'negative adsorption', indicating release of B2MG from cells into the plasma as blood passed through this filter. Comparison of reduction in plasma concentrations, sieving coefficients, plasma clearances and filter mass balances showed that the question of B2MG removal during hemofiltration is a complex issue where adsorption to the membrane, 'shedding' from blood cells, membrane pore size and possibly also 'redistribution' of B2MG in the body must be considered.

Interferon-γ for the treatment of metastatic renal cancer: Dose-dependent stimulation and downregulation of beta2 microglobulin and neopterin responses

Considering rIFN-γ as a potent biological response modifier (BRM), we started an open phase II trial with rIFN-γ in patients with advanced renal cell carcinoma (RCC).For optimization of the dose and schedule of rIFN-γ, two biochemical serum markers, neopterin and beta-2 microglobulin, were chosen to monitor the biological response.In order to test the magnitude and kinetics of rIFN-γ-induced neopterin and beta-2 microglobulin release in the serum, rIFN-γ was administered thrice at three different dose levels in a randomly assigned order (0.01; 0.1; 0.5 mg).Neopterin and beta-2 microglobulin were assessed by means of commercially available radioimmunoassays. The results revealed: 1) strong, reproducible and dose-dependent increments of both markers after the first injection 2) downregulation of the magnitude of neopterin responses with repeated injections at each of the three dose levels tested, and 3) a dose-dependent downregulation of the magnitude of beta-2 microglobulin responses and of serum baseline values at the highest dose level tested.From these data, we conclude that both the dose and schedule might be of importance for optimization of biological responses to exogenously applied rIFN-γ.

β<sub>2</sub>-Microglobulin Kinetics During Haemodialysis and Haemofiltration

Since the identification of beta 2-microglobulin as a major component of 'dialysis amyloid', concern about its removal by different dialysis methods has been raised. Haemodialysis with regenerated cellulose membranes increases serum beta 2-microglobulin by 10-15%. Serial measurements show a very early increase during cuprophan haemodialysis, the mechanism of which is as yet unknown. After cuprophan haemodialysis, serum values return to the initial pretreatment concentrations by the time of the next haemodialysis. In contrast to regenerated cellulose, dialysis with polycarbonate lowers serum beta 2-microglobulin by 8%, and dialysis with polysulphone by 53%. As opposed to cuprophan, after polysulphone haemodialysis the serum concentrations have not returned to the initial pretreatment levels within 48 h. Comparison of beta 2-microglobulin removal using the same polysulphone membrane for haemodialysis and haemofiltration shows that beta 2-microglobulin is more effectively removed by convection than by diffusion when both treatment modes are matched for blood flow and urea clearance. Therefore, in contrast to haemodialysis with regenerated cellulose membranes, where a transient, intradialytic release of beta 2-microglobulin is induced, significant removal is observed using higher permeable membranes. These findings may have implications for the generation of 'dialysis amyloid'.

Serum beta2-microglobulin in liver disease.

The concentration of beta 2-microglobulin in serum was determined in seventy-one patients with various liver disorders. Elevated values were found in most patients with chronic active or chronic persistent hepatitis and in over 80% of patients with alcohol-induced liver cirrhosis. In contrast, patients with alcohol-induced fatty liver, the serum beta 2-microglobulin concentrations were mostly within the normal range. Significant correlation (P less than 0.001) was noted between the elimination rate of galactose from blood and the serum beta 2-microglobulin concentration in patients with alcoholic liver damage but not in patients with chronic hepatitis. The reasons for the increased S-beta 2-microglobulin concentrations in liver diseases are unknown. Several explanations including a release of beta 2-microglobulin from necrotic liver cells or an increased synthesis of beta 2-microglobulin consequent to inflammation in the liver are possible. Alternatively, raised beta 2-microglobulin levels may reflect the hepatic synthesis during reparative growth.