Altered glycan accessibility on native immunoglobulin G complexes in early rheumatoid arthritis and its changes during therapy.

The goal of this study was to investigate the glycosylation profile of native immunoglobulin (Ig)G present in serum immune complexes in patients with rheumatoid arthritis (RA). To accomplish this, lectin binding assays, detecting the accessibility of glycans present on IgG-containing immune complexes by biotinylated lectins, were employed. Lectins capturing fucosyl residues (AAL), fucosylated tri-mannose N-glycan core sites (LCA), terminal sialic acid residues (SNA) and O-glycosidically linked galactose/N-acetylgalactosamine (GalNac-L) were used. Patients with recent-onset RA at baseline and after 3-year follow-up were investigated. We found that native IgG was complexed significantly more often with IgM, C1q, C3c and C-reactive protein (CRP) in RA patients, suggesting alterations of the native structure of IgG. The total accessibility of fucose residues on captured immune complexes to the respective lectin was significantly higher in patients with RA. Moreover, fucose accessibility on IgG-containing immune complexes correlated positively with the levels of antibodies to cyclic citrullinated peptides (anti-CCP). We also observed a significantly higher accessibility to sialic acid residues and galactose/GalNAc glyco-epitopes in native complexed IgG of patients with RA at baseline. While sialic acid accessibility increased during treatment, the accessibility of galactose/GalNAc decreased. Hence, successful treatment of RA was associated with an increase in the SNA/GalNAc-L ratio. Interestingly, the SNA/GalNAc-L ratio in particular rises after glucocorticoid treatment. In summary, this study shows the exposure of glycans in native complexed IgG of patients with early RA, revealing particular glycosylation patterns and its changes following pharmaceutical treatment.

Sialylation of anti-histone immunoglobulin G autoantibodies determines their capabilities to participate in the clearance of late apoptotic cells.

The Fc portion of immunoglobulin (Ig)G harbours a single glycosylation site. Glycan sialylation is critical for structure and for certain effector functions of IgG. Anti-histone IgG of patients with systemic lupus erythematosus is reportedly responsible for the recruitment of polymorphonuclear cells (PMN) to the clearance of apoptotic cells. Autoantibodies decorating secondary necrotic cells (SNEC) induce proinflammatory responses after activation of blood-borne phagocytes. Analysing the sialylation status of affinity-purified anti-histone IgG in patients with systemic lupus erythematosus (SLE), we demonstrated that the anti-histone IgG was contained preferentially in the non-sialylated fraction. In functional ex-vivo phagocytosis studies, non-sialylated anti-SNEC IgG directed SNEC preferentially into PMN but did not change their cytokine secretion profiles. In contrast, sialylated IgG reduced the phagocytosis by monocytes of SNEC. Moreover, the sialylated anti-SNEC IgG was not simply anti-inflammatory, but switched the cytokine secretion profiles from interleukin (IL)-6/IL-8 to tumour necrosis factor (TNF)-α/IL-1ß. Here we describe how different sialylation statuses of IgG autoantibodies contribute to the complex inflammatory network that regulates chronic inflammation.

Altered glycosylation of complexed native IgG molecules is associated with disease activity of systemic lupus erythematosus.

In addition to the redundancy of the receptors for the Fc portion of immunoglobulins, glycans result in potential ligands for a plethora of lectin receptors found in immune effector cells. Here we analysed the exposure of glycans containing fucosyl residues and the fucosylated tri-mannose N-type core by complexed native IgG in longitudinal serum samples of well-characterized patients with systemic lupus erythematosus. Consecutive serum samples of a cohort of 15 patients with systemic lupus erythematosus during periods of increased disease activity and remission were analysed. All patients fulfilled the 1982 American College of Rheumatology classification criteria. Sera of 15 sex- and age-matched normal healthy blood donors served as controls. The levels and type of glycosylation of complexed random IgG was measured with lectin enzyme-immunosorbent assays. After specifically gathering IgG complexes from sera, biotinylated lectins Aleuria aurantia lectin and Lens culinaris agglutinin were employed to detect IgG-associated fucosyl residues and the fucosylated tri-mannose N-glycan core, respectively. In sandwich-ELISAs, IgG-associated IgM, IgA, C1q, C3c and C-reactive protein (CRP) were detected as candidates for IgG immune complex constituents. We studied associations of the glycan of complexed IgG and disease activity according to the physician's global assessment of disease activity and the systemic lupus erythematosus disease activity index 2000 documented at the moment of blood taking. Our results showed significantly higher levels of Aleuria aurantia lectin and Lens culinaris agglutinin binding sites exposed on IgG complexes of patients with systemic lupus erythematosus than on those of normal healthy blood donors. Disease activity in systemic lupus erythematosus correlated with higher exposure of Aleuria aurantia lectin-reactive fucosyl residues by immobilized IgG complexes. Top levels of Aleuria aurantia lectin-reactivity were found in samples taken during the highest activity of systemic lupus erythematosus. Our results show that native circulating IgG complexes from active systemic lupus erythematosus patients expose fucosyl residues and their glycan core is accessible to soluble lectins. Two putative mechanisms may contribute to the increased exposure of these glycans: (1) the canonical N-glycosylation site of the IgG-CH2 domain; (2) an IgG binding non-IgG molecule, like complement or C-reactive protein. In both cases the complexed IgG may be alternatively targeted to lectin receptors of effector cells, e.g. dendritic cells.

[Genetic analysis of Drosophila melanogaster chromosome 3 neurodegenerative mutants induced with ethyl methanesulfonate].

Neurodegeneration, a pathological state accompanied by brain neuronal necrosis and changes in behavior, has been described for many animal species. However, the genetic control and molecular mechanisms of this process are yet vague. A large collection of neurodegenerative mutants of a model object, Drosophila melanogaster, can enhance understanding of these mechanisms. In this work, we have demonstrated that genetically determined anatomical changes in Drosophila brain are accompanied by a decreased lifespan and deviations from the wild-type sexual behavior and locomotor activity. It has been found that the genes vacuous and loechrig are candidates for molecular genetic analysis in eight mutants from the collection.

Glycosylation of random IgG distinguishes seropositive and seronegative rheumatoid arthritis.

The N-glycosylation of human immunoglobulins, especially IgGs, plays a critical role in determining affinity of IgGs towards their effector (pro- and anti-inflammatory) receptors. However, it is still not clear whether altered glycosylation is involved in only antibody-dependent disorders like seropositive rheumatoid arthritis (RA) or also in pathologies with similar clinical manifestations, but no specific autoantibodies like seronegative RA. The clarification of that uncertainty was the aim of the current study. Another study aim was the detection of specific glycan forms responsible for altered exposure of native glycoepitopes. We studied sera from seropositive RA (n = 15) and seronegative RA (n = 12) patients for exposure of glycans in native IgG molecules, followed by determination of specific glycans by capillary electrophoresis with laser-induced fluorescent detection (CE-LIF). Aged-matched groups of normal healthy donors (NHD) and samples of intravenous immunoglobulin IgG preparations (IVIG) served as controls. There was significantly stronger binding of Lens culinaris agglutinin (LCA) and Aleuria aurantia lectin (AAL) lectins towards IgG from seropositive RA compared to seronegative RA or NHD. CE-LIF analysis revealed statistically significant increases in bisecting glycans FA2BG2 (p = .006) and FABG2S1 (p = .005) seropositive RA, accompanied by decrease of bisecting monogalactosylated glycan FA2(6)G1 (p = .074) and non-bisecting monosialylated glycan FA2(3)G1S1 (p = .055). The results suggest that seropositive RA is distinct from seronegative RA in terms of IgG glycan moieties, attributable to specific immunoglobulin molecules present in seropositive disease. These glycans were determined to be bisecting GlcNAc-bearing forms FA2BG2 and FABG2S1, and their appearance increased the availability of LCA and AAL lectin-binding sites in native IgG glycoepitopes.

Anti-histone H1 IgGs possess proliferative activity towards human T-leukaemia CEM cells.

The aim of this study was to characterize the proliferative activity of the anti-histone H1 IgGs towards human T-leukaemia CEM cells. MATERIALS AND METHODS: Anti-histone H1 IgGs were purified from blood serum of systemic lupus erythematosus patients by precipitation of serum proteins with 50% ammonium sulfate followed by a sequential affinity chromatography on Protein G-Sepharose and histone H1-Sepharose columns. To avoid contamination with other proteins, anti-histone H1 IgGs were subjected to strongly acidic pH 2.0 during gel filtration through HPLC column. The effects of the anti-histone H1 IgGs on cell viability and cell cycle were tested by MTS-assay and flow cytometry, correspondingly. The cross-reactivity of the anti-histone H1 antibodies towards heterogenetic and cellular antigens was evaluated by Western-blot analysis. RESULTS: It was found that incubation of CEM cells with the HPLC-purified anti-histone H1 IgGs resulted in significant stimulation of cell growth by 46% after 48 h of incubation. These IgGs possess an antigenic poly-specificity to positively charged heterogenetic antigens and different cellular antigens. FITC-labeled and biotinylated anti-histone H1 IgGs are internalized by CEM cells and preferentially accumulated in the cytoplasm. CONCLUSION: The anti-histone H1 IgGs are shown to internalize human T-leukemia CEM and stimulate their proliferation. These IgGs are polyspecific toward cellular antigens.

Blood serum immunoglobulins of patients with multiple myeloma are capable of hydrolysing histone H1.

BACKGROUND: Recently we have shown that the imunoglobulins G from blood serum of some multiple sclerosis patients are capable of cleaving histone H1. AIM: To check whether histone H1-hydrolyzing abzymes could be detected not only in blood plasma of autoimmune patients, but also during cancer development, particularly during the onset of multiple myeloma. METHODS: Immunoglobulines were isolated from blood serum of multiple myeloma patients (n = 11) by precipitation with 50% ammonium sulfate and tested for proteolytic activity toward linker and core calf thymus histones. Antibody preparations able to cleaved histone H1 were subjected to affinity chromatography on histone H1-Sepharose with following analysis of chromatographic fractions' protease activity. To prove that antibody molecules are responsible for hydrolysis of histone H1, gel filtration at acidic pH with subsequent examination of protease activity of chromatographic fractions (pH-shock analysis) was used. RESULTS: It was found that 3 of 11 antibody preparations are capable of hydrolyzing calf thymus histone H1 but not core histones. It was shown that histone H1-hydrolysing activity of 2 proteolytically active antibody preparations is associated with IgGs that possess affinity towards histone H1. pH-shock analysis proved that protease activity towards histone H1 is intrinsic property of IgG molecules. CONCLUSIONS: We demonstrated the existence of previously unknown histone H1 hydrolyzing IgG abzymes in the serum of multiple myeloma patients. Possible biological role of hisH1-hydrolyzing antibodies in patients with multiple myeloma was discussed.