Enrichment of antibodies against phospholipids in circulating immune complexes (CIC) in the anti-phospholipid syndrome (APLS)

The aim of this study was to analyse and characterize immunoglobulins in CIC and serum from patients with anti-cardiolipin antibodies. CIC from five patients were isolated by gradient centrifugation and gel filtration. The distribution between serum and CIC of immunoglobulin reactivity against different phospholipids was determined. Serum and CIC contained antibodies against cardiolipin and other negatively charged phospholipids. The relative concentration of these antibodies was higher in the immune complexes than in corresponding sera, and the avidity of antibodies in immune complex form was higher. The presence of high concentrations of antibodies to negatively charged phospholipids in CIC from patients with anti-cardiolipin antibodies could be of pathogenic significance in APLS by conferring characteristics to the complexes of importance for binding to membrane components. This could have special implications with regard to platelet and complement activation, thrombocytopenia and thrombophilia.     

Presence of antibodies reacting specifically with structural proteins of mouse mammary tumor virus (MMTV) among antibodies composing circulating immune complexes in breast cancer patients

All-Union Oncologic Scientific Center, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. N. Trapeznikov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 105, No. 4, pp. 475–477, April, 1988.     

补体C5b-9抗血清对抗胸腺细胞血清性肾炎大鼠肾组织一氧化氮合成及其病变的影响

目的: 探讨抗鼠补体C5b-9复合物抗血清对系膜增生性肾炎大鼠肾组织合成一氧化氮 (NO)及其病变的作用。方法: 复制大鼠系膜增生性肾小球肾炎即抗胸腺细胞血清性肾炎 (ATSN)模型 ,用抗大鼠C5b-9复合物抗血清处理 ,观察其对ATSN大鼠NO相关指标及其病变的影响。结果: 抗鼠C5b-9复合物抗血清既能减少ATSN大鼠肾组织诱生性NO合酶 (iNOS)mRNA的表达和大鼠尿液中硝酸盐 /亚硝酸盐 (NO₃^- /NO₂^- )排泄量 ,还能减低大鼠肾组织病变的程度。NOS抑制剂L -NAME也可降低尿NO₃^- /NO₃^- 排泄量 ,同时减轻肾组织病变程度。结论: 抗鼠C5b-9复合物抗血清能够抑制肾细胞NO的合成及其肾小球系膜细胞的增生。     

Quantification of human immunoglobulins by semiautomatic polyethylene glycol precipitation radioimmunoassays. Estimation of circulating immune complexes and immunoglobulin synthesized in vitro

Simple, reliable semiautomatic radioimmunoassays have been developed for the measurement of human immunoglobulins (IgG, IgA, IgM, IgK and Ig lambda). The assays are based on the separation of free from antibody-bound radiolabelled fragments of immunoglobulin by precipitation with 13% polyethylene glycol. The precipitate is harvested and washed on glass fibre filters by means of a commercial cell harvester. Radiolabelled lambda chain from Bence Jones urine was used for lambda chain assay and Fab' gamma from pooled IgG for the kappa assay. Labelled Fab or Fc fragments of IgG, IgA and IgM were used for the class specific assays. Selected commercial antisera were used throughout. The sensitivity limits of the assays performed according to the standard procedure were about 20 ng Ig per ml. The assays have been used for the quantification of circulating immune complexes and both cellular and secreted immunoglobulin produced in cell cultures. The results demonstrate the importance of the simultaneous quantification by L chain and H chain specific assays.     

A method for quantitative determination of average masses and concentrations of circulating immune complexes in human sera

A method for rapid determination of average masses and concentrations of circulating immune complexes in human sera is suggested. It is based on the dissimilarity in solubilities of immune complexes with different masses in the presence of polyethyleneglycol. Light-scattering intensities are measured by a laser nephelometer after adding to the serum of PEG in two different concentrations. The experimental values of the average masses and concentrations are calculated using calibration curves. The calibration curves are plotted for model immune complexes with different average masses obtained by heat-aggregation of IgG at various concentrations. This technique has been employed for determination of the average masses and concentrations of circulating immune complexes in 17 patients suffering from systemic lupus erythematosus and in 8 control individuals.     

Advantages of sequential polyethylene glycol (PEG) precipitations to isolate and analyze circulating immune complexes

The present report describes a new approach utilizing sequential polyethylene glycol 6000 (PEG) precipitations to isolate and analyze circulating immune complexes (IC). Two experimental systems were studied. First, IC were formed by adding labeled or unlabeled bovine serum albumin (BSA) to anti-BSA antiserum. Sequential precipitations with PEG concentrations ranging from 2 to 6.2 indicated that immunoglobulin (Ig) molecules were precipitated in all experimental and control sera tested. In contrast, optimal precipitations of IC (i.e., highest BSA/Ig ratio) were a function both of PEG concentration and of BSA/anti-BSA ratio (i.e., of IC size). Satisfactory IC purification was achieved by precipitation with appropriate PEG concentration followed by incubation with STaphylococcus aureus, Cowan I. Second, in preliminary experiments, the same procedure was applied to human sera. The findings paralleled those of the BSA/anti-BSA system. While PEG precipitated Ig in all sera tested, a potential antigen was found only in the most IC-positive serum, and only at the higher of the two PEG concentrations tested. From our data, we conclude that PEG concentrations needed to precipitate IC cannot be predetermined, as they are a function of the size and probably the nature of the IC studied. This limitation can be overcome by the systematic sequential precipitations which increase the chances of identifying antigens and decrease the risks of confusing antigen-antibody complexes and Ig aggregates.     

Immune complex-like moieties in immunoglobulin for intravenous use (IVIg) bind complement and enhance phagocytosis of human erythrocytes

Treatment with IVIg can, on rare occasions, lead to detrimental effects such as enhanced erythrocyte sequestration and an increase in serum immune complexes with inflammatory sequellae such as exacerbation of glomerular nephritis. In this study, IVIg (Sandoglobin) was examined for complement binding moieties which resemble immune complexes and can mediate the binding of IgG and C′3b to human erythrocytes via CR1 and enhance erythrocyte susceptibility to sequestration. Sephacryl S-200 HR separated IVIg into two fractions: monomeric IgG (74%) and larger complexes of the molecular weight of an IgG dimer or greater (≥ 300 kD) (26%). In the presence of complement, the ‘dimers’ bound to human erythrocytes, rendering them susceptible to phagocytosis in vitro. Removal of erythrocyte-specific isoantibodies from the IVIg had no effect on ‘dimer’ binding to the erythrocytes. Monomeric IgG contained virtually no complement-activating, erythrocyte-binding activity. Erythrocyte binding of complement-bearing IgG ‘dimers’ and subsequent phagocytosis resembles the binding of complement-bearing immune complexes to erythrocyte CR1. Exposure to Factor I leads to the release of complement-bearing IgG ‘dimers’ from erythrocyte CR1 and to the abrogation of erythrophagocytosis. Binding of complement-bearing IgG ‘dimers’ to the erythrocyte is blocked by To5, a CR1-specific monoclonal antibody.     

Influence of serum complement and rheumatoid factor on detection of immune complexes by the C1q and monoclonal rheumatoid factor solid-phase assay

Soluble purified monoclonal and polyclonal rheumatoid factor, total serum complement, and soluble C1q all inhibit the detection of model tetanus toxoid/anti-toxoid immune complexes in the solid-phase C1q assay. The binding of these immune complexes to solid-phase monoclonal rheumatoid factor is less inhibited by soluble C1q and by total serum complement, but clearly decreased by soluble monoclonal or polyclonal rheumatoid factor. Serum complement does not reduce the size of these model complexes. We recommend the use of low ionic strength EDTA (10 mM) to partly neutralize the complement-mediated inhibition. This procedure is shown to be superior to currently used higher EDTA concentrations and to the use of IgG-Sepharose.     

Effect of plasmapheresis on ligand binding capacity and expression of erythrocyte complement receptor type 1 (CR1) of patients with systemic lupus erythematosus (SLE)

The functional activity and the expression of CR1 on the erythrocytes (E) of patients with SLE were, respectively, determined by measuring the binding to E of either complement-opsonized bovine serum albumin (BSA)-anti-BSA immune complexes (ICC) or specific anti-ECR1 MoAbs. We found that both the functional activity and levels of ECR1 in SLE patients homozygous for ECR1 high density allele were significantly lowered compared with healthy controls having the same allele. Soon after plasmapheresis there was a significant increase in E ICC binding activity, and this increased functional activity was stable. Moreover, plasmapheresis reduced the level of immune complexes demonstrable in the circulation of the patients. The expression of ECR1 determined with several different anti-CR1 MoAbs was also elevated as a consequence of plasmapheresis. This elevation was observed for both MoAb 1B4, which competes for the ICC binding site of ECR1, and for MoAb HB8592, which does not, but the time course for the increase in binding of the two MoAbs was different, in that the epitope recognized by MoAb 1B4 increased more rapidly. The present results, considered in the context of previous findings, suggest that more than one mechanism may be operative with respect to the effects of the plasmapheresis in increasing ECR1 levels defined by different epitopes on the molecule.     

Immunofluorescence studies on the codistribution immune deposits and complement in the thyroid glands of Obese strain (OS) chickens

This study demonstrates immune complexes in thyroid glands of Obese strain (OS) chickens, that consist of thyroglobulin (Tg) and antibodies to Tg. In IIF tests it was shown that these complexes fix complement with an age-dependent increase from 12% in 19-day-old embryos up to 100% in 6-week-old animals. This finding and the observation that the deposition of complement-binding immune complexes precede cellular infiltration of the thyroid gland and correlate with the serum titer of Tg-Ab (as one parameter of the disease) points towards a role as one initial effector mechanism for the development of spontaneous autoimmune thyroiditis (SAT).     

Individual sequence variability and functional activities of fibrinogen-related proteins (FREPs) in the Mediterranean mussel (Mytilus galloprovincialis) suggest ancient and complex immune recognition models in invertebrates

In this paper, we describe sequences of fibrinogen-related proteins (FREPs) in the Mediterranean mussel Mytilus galloprovincialis (MuFREPs) with the fibrinogen domain probably involved in the antigen recognition, but without the additional collagen-like domain of ficolins, molecules responsible for complement activation by the lectin pathway. Although they do not seem to be true or primive ficolins since the phylogenetic analysis are not conclusive enough, their expression is increased after bacterial infection or PAMPs treatment and they present opsonic activities similar to mammalian ficolins. The most remarkable aspect of these sequences was the existence of a very diverse set of FREP sequences among and within individuals (different mussels do not share any identical sequence) which parallels the extraordinary complexity of the immune system, suggesting the existence of a primitive system with a potential capacity to recognize and eliminate different kind of pathogens.     

Influence of the electric charge of the antigen and the immune complex (IC) lattice on the IC activation of human complement

In order to understand the mechanism of complement (C) activation by immune complexes (ICs), the anti-complementary effect of ICs containing cationized antigens was compared in vitro to that using ICs formed by native antigens. ICs were prepared with affinity-purified rabbit polyclonal IgG antibovine serum albumin (BSA) antibody and either native BSA (isoelectric point 4.2) or BSA rendered cationic by treatment with ethylenediamine (isoelectric point 9.4). Native and cationized antigens were characterized by isoelectric focusing. ICs containing anti-BSA IgG or F(ab')2, formed either at equivalence or in excess of native or cationized antigen, were submitted to ultracentrifugation in a sucrose gradient for mesh size determination. The anti-complementary effect of ICs was evaluated by kinetic determination of haemolytic activity of human serum on haemolysin-sensitized sheep red blood cells. In conditions of antigen excess, the ICs formed by cationized BSA were significantly more efficient in activating human complement than those formed by native antigen. This higher activity was dependent on cationized antigen complexed with complete antibody molecules, as non-complexed cationized BSA or ICs prepared with F(ab')2 fragments were inactive under the same experimental conditions. Furthermore, this difference did not depend on the mesh size of the immune complexes. Our results suggest that the balance between antigen, antibody and C may be of importance in vivo for the onset and course of infections and other pathological processes involving IC formation. ICs containing cationized antigens should be proven of value in experimental models for studies on the regulation of C activation.     

The effects of marathon running on expression of the complement regulatory proteins CD55 (DAF) and CD59 (MACIF) on red blood cells

Exercise is known to result in the haemolysis of red blood cells (RBCs). Although mechanical stressors such as footstrike and an increased velocity of blood flow may be involved, the biological mechanisms that underpin RBC haemolysis remain elusive. RBCs are potentially susceptible to lysis by autologous complement activation. RBCs are protected from the lytic effects of complement by regulatory proteins (CRPs) bound to the cell membrane via glycosylphosphatidylinositol (GPI) anchors. This study aimed to determine if marathon running would result in RBC haemolysis through a loss of membrane expression of the CRPs CD55 (decay accelerating factor) and CD59 (membrane attack complex inhibitory factor). Blood samples were obtained from 14 male runners before, within 30 min after, and 24 h after completion of the 2004 London Marathon. RBCs were assessed for cell surface CD55 and CD59 expression using indirect immunofluorescence assays and flow cytometry. No significant changes in the total RBC count, haematocrit or haemoglobin concentrations were found in response to running the marathon (P > 0.05). Blood bilirubin concentrations after the marathon were significantly greater than the pre-race values (P < 0.01). The relative fluorescent intensity (arbitrary units) of CD55 and CD59 expression on RBC membranes did not change in response to the marathon race (P > 0.05). In conclusion, marathon running did not alter the expression of CD55 or CD59 on RBCs, despite concomitant elevations in blood bilirubin concentrations. Consequently, any haemolysis of RBCs that occurred in response to the marathon was not likely due to a loss of membrane bound CRPs and subsequent cell lysis by autologous complement.     

Effects of systemicin vivo interleukin-2 (IL-2) reconstitution in patients with acquired immune deficiency syndrome (AIDS) and AIDS-related complex (ARC) on phenotypes and functions of peripheral blood mononuclear cells (PBMC)

In the context of a clinical phase I/II therapy study with recombinant interleukin-2 (rIL-2), we monitored immunological alterations in four patients with acquired immune deficiency syndrome (AIDS) and three patients with AIDS-related complex (ARC). By determining the surface phenotypes andin vitro functions of peripheral blood mononuclear cells (PBMC) before, during, and after treatment with rIL-2, we observed transient changes in all important leukocyte subpopulations, a minor restoration of immune reactivityin vitro, and an improvement in skin reactivityin vivo. In particular, we found (i) a transient increase in C3b receptor-mediated monocyte activation in ARC patients; (ii) no influence of therapy on the otherwise intact LPS-induced interleukin-1 productionin vitro; (iii) in some patients a transient corrective influence on the high pretherapeutic immunoglobulin secretion of B cells and their nonresponsiveness to pokeweed mitogen; (iv) low T-cell responses to soluble antigens and alloantigens, which were partially restored during rIL-2 treatment in ARC patients and in one AIDS patient; (v) defective NK activity in PBMC of two AIDS patients, which was found to be restored when measured at the end of rIL-2 therapy; and (vi) a rather constant phenotypic pattern of PBMC in each patient during therapy except for the decreasing proportion of OKT9-positive lymphocytes in AIDS patients, the increasing proportion of Leu8^–Leu3a⁺ lymphocytes in all patients, and in particular, the transient significant decrease in the Leu7⁺/OKT3⁺ ratio, which pretherapeutically was very high in AIDS patients (0.78±0.21) and high in ARC patients (0.48±0.06) as compared to healthy controls (0.18±0.08).Dedicated to Prof. Dr. Dr. h. c. Otto Westphal, who continuously supported and encouraged cooperation of basic and clinical immunologists.     

Phenotypical and functional analysis of B lymphocytes of two siblings with combined immunodeficiency and defective expression of major histocompatibility complex (MHC) class II antigens on mononuclear cells

Phenotypic and functional analysis of B lymphocytes in two siblings with combined immunodeficiency associated with defective expression of class I and class II major histocompatibility complex (MHC) antigens on mononuclear cells is described. The results of the analysis of the membrane phenotype of the B cells performed at the age of 1 and 5 years, respectively, by the use of monoclonal antibodies against class I (HLA-A, -B, -C) and class II (HLA-DR, -DP, -DQ) MHC antigens showed a decreased expression of class I antigens and a complete lack of class II antigens. Class I antigen expression consistently remained of the same magnitude during follow-up. Class II antigen expression remarkably had been positive early in life on B cells and activated T cells, whereas monocytes were negative for class II from birth onward. B lymphocytes of both patients respondedin vitro to polyclonal activation withStaphylococcus aureus Cowan I staphylococci (SAC) with the production of IgM-type immunoglobulins only. This neonatal type of response was in agreement with the membrane immunoglobulin phenotype of the B cells since a high sIgM/sIgD ratio characteristic of neonatal B cells was present. However, the expression of the FMC7 antigen on B cells of both patients was comparable to that on B cells of normal adults. We hypothesized that the lack of MHC antigen expression may impose a resting state on the lymphocytes in these patients due to ineffective cellular interactions. In this view the high sIgM/sIgD ratio reflects the activation state of the B cells rather than the maturational state of the cells. Furthermore, the B cells of these patients did not produce antipolysaccharide antibodies upon simultaneous stimulation with SAC and pokeweed mitogen (PWM). In the youngest child (age 1 year) this may reflect the unresponsiveness to polysaccharide antigens usually observed in children less than 2 years old. In the eldest child the nonresponsiveness might reflect a more general B-cell defect as a result of waning B-cell function increasing with age and imposed by lack of effectivein vivo activation.     

The complement regulatory proteins CD55 (decay accelerating factor) and CD59 are expressed on the inner acrosomal membrane of human spermatozoa as well as CD46 (membrane cofactor protein)

The complement regulatory proteins CD55 and CD59 are expressed on the plasma membrane of human spermatozoa, whereas CD46 is only on the inner acrosomal membrane (IAM) which becomes surfaced exposed after the acrosome reaction when sperm assume fertilisation-competence. CD55 & CD59, two glycosylphosphatidylinositol (GPI)-anchored proteins, have been detected previously in some studies also in the acrosomal region of chemically fixed spermatozoa but never demonstrated at this site on unfixed spermatozoa. Dual labelling immunofluorescence and confocal microscopy on fresh unfixed spermatozoa, with minimal subsequent time to fixation, has shown CD55 to be markedly expressed on the IAM, more than on the plasma membrane. However, unlike for CD46, CD55 displayed patchy staining over the acrosome, with some variation between individual spermatozoa. All IAM-associated CD55 was localised within GM1-containing lipid rafts. CD59 was expressed also on the IAM, but in a pronounced granular pattern with more variation observed from one spermatozoa to another. Both CD55 & CD59 were released from the IAM by PI-PLC, demonstrating them to be GPI-anchored. Analysis of acrosome-reacted spermatozoal CD55 by Western blotting revealed a novel single 55 kDa protein lacking significant oligosaccharides susceptible to glycosidases. Antibody-induced membrane rafting and release of CD55 & CD59 in vitro may have influenced previous results. Significant coexpression of CD55 & CD46 on the IAM suggests some functional cooperation at this site.     

Detection and quantitation of hepatitis-B surface antigen immune complexes (HBsAg-ICs) by an antigen-specific method. I. Detection and quantitation of in vitro prepared HBsAg-ICs

An antigen-specific method has been developed for direct detection and quantitation of HBsAg-ICs. The method involves (1) precipitation of HBsAg-ICs with 3.5% PEG; (2) dissociation of the PEG precipitated ICs by treatment with NaSCN, NaI, KBr, low or high pH buffers, trypsin or papain; and (3) detection and titration of HBsAg and/or anti-HBs liberated from ICs. Treatment with 2 M and 3 M NaSCN, papain or trypsin liberates HBsAg, while following treatment with 3 M and NaI free anti-HBs is detectable. Trypsin digestion (2 mg/ml, 30 min at 37 degrees C) proved to be most effective for disrupting HBsAg-ICs formed at equivalence as well as in excess of antigen or antibody. After trypsin digestion of the sample RPHA, RIA and ELISA may be used as a third step. Th