Serum Levels Of Immune Complexes Research Articles

#2314 Circulating immune complexes concentration and complement activation in sensitized kidney transplant recipients

Abstract Background and Aims Chronic antibody mediated rejection of the kidney transplant is the most common cause of graft loss in the late posttransplant period. Crucial in this process seems to be the role of classical pathway complement activation due to the formation of immune complexes. The formation of immune complexes is a benign process of a normally functioning immune system. In kidney transplant recipients (KTRs), the production of donor specific IgG/IgM antibodies (DSAs) against donor antigens (MHC molecules, ABO blood group antigens) leads to the attachment of immune complexes to cell membranes and subsequent tissue damage through complement activation. The attachment of C1q complement fragment to the immune complexes holds an important part in this process. This study aims to determine the levels of immune complexes as well as classical pathway complement activation in sensitized kidney transplant recipients. Method In this cross-sectional study 3 groups of KTRs were compared as to the levels of immunocomplexes concentration and classical pathway complement activation. Fourteen KTRs with preformed or de novo donor specific antibodies were compared to 28 kidney transplant recipients with no DSAs and to 22 subjects with no history of chronic kidney disease (controls). We used MicroVue Complement CIC-C1q EIA that is designed to detect immunocomplexes that bind to C1q in human serum or plasma. In order to estimate total classical pathway complement activation in serum, we used MicroVue Complement CH50 Eq EIA. Results Kidney function (eGFR) of KTRs with and without DSAs was similar (53.1 ± vs. 60.8 ± ml/min/1.73 m2, p = 0.54) but lower in comparison to controls (106.4 ml/min/1.73 m2, p < 0.001). We found a significantly higher concentration of C1q-immunocomplexes in the serum of KTRs with donor specific antibodies, in comparison to controls, as well as to the group of kidney transplant recipients with no DSAs (6.78 ± 2.7 vs. 4.83 ± 1.9 vs. 5.04 ± 1.2 μgEq/ml respectively, p = 0.0078). Furthermore, there was no significant difference of C1q-immunocomplexes between kidney transplant recipients with no DSAs and controls. Finally, a significant reduction of CH50 levels was observed in KTRs with DSAs as compared to controls and KTRs with no DSAs (39.2 ± 14.9 vs. 70.6 ± 34.3 vs. 67.9 ± 39.9 U/ml respectively, p = 0.003), which suggests higher levels of classical pathway complement activation. CH50 levels in KTRs with DSAs, who were further subcategorized in those with preformed and those with de novo DSAs were similar (39.68 ± 15.6 vs 39.08 ± 16.04 U/ml). Conclusion Kidney transplant recipients with donor specific antibodies have increased serum levels of immune complexes and increased classical pathway complement activation.

Carotid intima media thickness and blood biomarkers of atherosclerosis in patients after stroke or myocardial infarction.

AimTo test if circulating levels of markers of inflammation, endothelial function, and chronic infections, as well as association between these markers and carotid intima media thickness (CIMT), depend on the stage of atherosclerosis expressed as a history of a major vascular event.MethodsThe associations were analyzed separately in 75 healthy controls, 79 patients 3-6 months after the first-ever non-cardioembolic ischemic stroke (IS), and 37 patients 3-6 months after the first-ever myocardial infarction (MI). Data were collected prospectively in 2005. We measured high sensitivity C-reactive protein (hs-CRP), procalcitonin, E-selectin, intercellular adhesion molecule-1 (ICAM-1), serum level of immune complexes (IC), and identified antibodies against Herpes simplex virus type 1 (HSV), Cytomegalovirus, Chlamydia pneumonia, and Helicobacter pylori. Correlations with CIMT were determined using Pearson R and verified after adjustment for age, sex, hypertension, diabetes, and statin therapy.ResultsMedian ICAM-1 concentration was significantly lower in controls than in post-IS patients (188 μg/L vs 215 μg/L), and significantly lower in post-IS patients than in post-MI patients (215 μg/L vs 260 μg/L). Control patients also had significantly lower IC level (0.03 U/L) and HSV antibody index (6.0) compared to both post-IS (0.6 U/L, 9.6) and post-MI (0.4 U/L, 9.2) patients. CIMT was correlated with age (Pearson R = 0.38, P = 0.001) in the control group, immune complexes (R = 0.26, P = 0.023) in the post-IS group, and with hs-CRP (R = 0.40, P = 0.017) in the post-MI group. These correlations were confirmed using multiple regression analysis.ConclusionsOur study supports linear correlations between CIMT and IC and hs-CRP levels. However, these associations seem to depend on the type of vascular burden.

Normal serum levels of immune complexes in postpolio patients

ObjectiveThe pathophysiology of the postpolio syndrome is not fully understood. Increased cytokine levels in cerebrospinal fluid and peripheral blood indicate a systemic inflammatory process. Decreased cytokine levels and the clinical effect of intravenous immunoglobulin treatment further indicate an inflammatory/immunological pathogenesis. The aim of the present study was to evaluate whether an autoimmune process follows the initial infection, by means of analyzing immune complexes. Patients and methodsCirculating immune complexes were analyzed from blood samples of 20 postpolio patients and 95 healthy controls. To compensate for differences in age between patients and controls, a sub-analysis was performed using only the 30 oldest controls. Tumor necrosis factor-inducing properties of polyethylene glycol-precipitated immune complexes were compared between the postpolio patients and 10 healthy controls. ResultsWhen comparing levels in postpolio patients to the whole control group, including the 30 oldest investigated, there were no statistically significant differences. No difference was found in tumor necrosis factor levels induced by immune complexes when comparing patients and controls. ConclusionsThere was no increase in circulating immune complex or in tumor necrosis factor-inducing effects of circulating immune complex between postpolio patients and healthy controls, indicating that the postpolio syndrome is not due to an autoimmune reaction.

In vitro-generated immune complexes containing galactose-deficient IgA1 stimulate proliferation of mesangial cells

IgA nephropathy (IgAN) patients have elevated serum levels of immune complexes consisting of IgA1 with galactose-deficient hinge-region O-glycans (Gd-IgA1) and anti-glycan IgG. These immune complexes deposit in the kidney and activate mesangial cells. To confirm that the activity of these immune complexes depends on the interaction of Gd-IgA1 with anti-glycan IgG, we generated in vitro analogous immune complexes using Gd-IgA1 myeloma protein and anti-glycan IgG from cord blood of healthy women. The Gd-IgA1 and anti-glycan IgG from cord-blood serum formed IgA1–IgG immune complexes that resembled those in sera of patients with IgAN. Furthermore, the ability to activate cellular proliferation was dependent on a heat-sensitive serum factor. In summary, we developed a new protocol for in-vitro formation of IgA1–IgG immune complexes, thus providing a new tool for studies of the pathogenesis of IgAN.

Spontaneous in vitro production of rheumatoid factor during infectious exacerbations of cystic fibrosis: correlation with circulating immune complex levels.

Rheumatoid factor (RF) production has been demonstrated during infections, including infectious exacerbations of cystic fibrosis (CF). The aim of this study was to evaluate the relationship of RF production to infection, and examine the mechanisms involved. Serial peripheral blood mononuclear cell (PBMC) cultures with measurement of spontaneous production of IgM RF, IgA RF, total IgM and IgA, and measurement of serum levels of immune complexes were carried out during exacerbations of CF. The percentage of B cells expressing CD5 was examined in a second cohort of acutely infected CF patients, and related to IgM RF production. IgM RF production was significantly elevated during acute infection compared with convalescence (P < 0.05), stable CF subjects (P < 0.005) and normal controls (P < 0.05). IgM RF production did not correlate with total IgM production in the majority of patients, but was closely related to circulating immune complex levels in 8/10 subjects. IgA RF production did not increase significantly during infection, and did not correlate with total IgA or IgM RF production, or with circulating immune complex levels. CD5+ B cells were not increased in the CF group, and the percentage of CD5+ B cells did not correlate with IgM RF synthesis. These observations suggest that RF production during infection is specifically induced, possibly by immune complex autoimmunization, and is not simply the result of polyclonal B cell activation. Different patterns of IgM RF and IgA RF synthesis suggest different mechanisms of induction.

Therapeutic effect of 15-deoxyspergualin on the progression of lupus nephritis in MRL mice. I. Immunopathological analyses

The effect of 15-deoxyspergualin (DSP), a newly developed immunosuppressive agent, on the development of spontaneously occurring lupus glomerulonephritis in MRL-lpr mice was examined. Administration of the drug was initiated at the age of 13 or 17 weeks, when polyclonal B cell activation and lupus nephropathy were apparent or became prominent. Treatment with DSP for up to 19 weeks of age at a dose of 2 mg/kg twice a day or 5 mg/kg daily strongly suppressed the increment of IgG-producing cell numbers in the spleen and serum levels of immune complexes and anti-DNA antibodies. Glomerular histological score estimated by light microscopy and IgG and C3 deposition in renal glomeruli were improved, compared with untreated control mice. Thus, DSP was shown to suppress the progression of polyclonal B cell activation and lupus nephropathy in MRL/lpr mice. These results suggest that DSP may be used as a therapeutic agent for systemic lupus erythematosus.

Myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA)-positive microscopic polyarteritis (MPA) associated with Hashimoto's thyroiditis and increased serum rheumatoid factor

An autopsy case of microscopic polyarteritis (MPA) associated with Hashimoto's thyroiditis that showed glomerular immunoglobulin and complement depositions and high titers of rheumatoid factor and myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA) is reported. A 72-year-old woman was admitted to our hospital because of renal failure that had deteriorated from a serum creatinine value of 175.8 to 1874.1 μmol/l in 4 weeks. Laboratory studies on admission revealed proteinuria, numerous red blood cells, granular casts and red blood casts in the urine, increased serum blood urea nitrogen (47.8 mmol/l), anemia (hemoglobin, 60 g/l), and thrombocytopenia (platelets, 71 × 109/l). Emergency hemodialysis was started; however, the patient died on the fifth hospital day because of ventricular tachycardia, and an autopsy was performed. At autopsy, the patient was found to have had increased serum levels of immune complexes, rheumatoid factor, IgG rheumatoid factor, myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA), anti-thyroglobulin antibody, and anti-thyroid peroxidase antibody, and decreased serum complement levels. Microscopic examination revealed crescentic glomerulonephritis in almost all glomeruli, and positive granular deposits of IgG, IgA, IgM, C1q, C3, and C4 in the mesangium and along the capillary walls. Typical fibrinoid necrosis was found in the small arteries of the stomach, colon, small intestine, and bladder. Finally, Hashimoto's thyroiditis was noted. To our knowledge, this is the first case of MPO-ANCA-positive MPA associated with Hashimoto's thyroiditis and increased serum rheumatoid factor levels.

Involvement of Immunopathogenic Mechanisms in a Spontaneously Occurring Glomerulopathy in Mice

Mice have been found to be susceptible to spontaneous renal localization of immune deposits. However, the significance of these immune deposits is still debated. We investigated the immunopathogenesis of a naturally occurring glomerulopathy associated with progressive proteinuria and glomerulosclerosis in 75 BALB/c mice. The mice were divided into five groups of 15 and killed at the age of 1, 3, 6, 12, or 18 months for laboratory and renal pathologic studies. These mice showed persistently increasing serum levels of immune complexes, a marked increase of glomerular immune deposits which were capable of fixing C3, and interstitial infiltration of lymphocytes and plasma cells, followed by the occurrence of proteinuria, mesangiopathy, and glomerulosclerosis. Our findings suggest that an immune system mediated process occurred in the kidneys of the mice tested.

Predictive value of IgG autoantibodies against C1q for nephritis in systemic lupus erythematosus.

Antibodies against C1q (C1qAb) have been demonstrated in the serum of patients with several immune complex diseases. Patients, particularly those with lupus nephritis, were found to have increased serum titres of IgG C1qAb in a cross-sectional analysis. In the present prospective study correlations were sought between serum titres of IgG C1qAb and clinical as well as laboratory parameters of disease activity in patients with systemic lupus erythematosus (SLE). Titres of IgG C1qAb in the serum of 68 SLE patients were measured serially during a three year period. At the same time clinical and laboratory parameters of disease activity were assessed. Increased titres of IgG C1qAb were found in the serum of 56% of SLE patients during the study. Significant correlations were found between increased titres of IgG C1qAb and renal involvement. Clinical signs of renal involvement were found to be associated with significant increases of serum titres of IgG C1qAb in the six months preceding this appearance. Fifty per cent of the increases in serum titres of IgG C1qAb were followed by the development of renal involvement. Elevated serum titres of IgG C1qAb were especially related to proliferative forms of glomerulonephritis. Furthermore, significant correlations were found between serum titres of IgG C1qAb and serum levels of immune complexes, levels of complement components, and titres of antibodies to DNA. The results suggest that IgG C1qAb play a pathogenic role in the development of lupus nephritis and that serial measurement of serum titres of IgG C1qAb is useful in the management of SLE patients.

Immunological abnormalities in family members of patients with IgA nephropathy.

We examined several immunological parameters such as the number of T cells with CD4 antigen and the receptor for the Fc portion of IgA (T alpha cells), in vitro immunoglobulin production by peripheral blood lymphocytes with or without pokeweed mitogen and serum levels of immune complexes in 19 healthy family members of patients with IgA nephropathy (IgAN). It was shown that the levels of serum IgA, T4 cells, CD4/CD8 ratio of T cell subsets, T alpha cells, IgA circulating immune-complexes and spontaneous synthesis of immunoglobulins were significantly increased in family members of patients with IgAN. No family members had proteinuria or hematuria. It was concluded that immunological abnormalities, including abnormalities of T cells and B cells, were found not only in patients with IgAN but also in their healthy family members. It was suggested that some factors in addition to these immunological abnormalities may be involved in the development of IgAN.

Demyelinating neuropathy associated with hepatitis B virus infection: Detection of immune complexes composed of hepatitis B virus surface antigen

We observed 4 patients with the Guillain-Barré syndrome (GBS) type of polyneuropathy and one patient with chronic relapsing polyneuropathy associated with hepatitis B virus infection, and examined the sera, cerebrospinal fluid (CSF) and sural nerve specimens from the patients in search of the pathogenetic factors involved. It was demonstrated that hepatitis B surface antigen(HBsAg)-immune complexes were significantly increased in both the sera and the CSF of the 4 patients with GBS. The serum levels of immune complexes were also closely related to the clinical status of these patients. In all patients, HBsAg-positive labelling of immunofluorescence was found around the endoneural small blood vessels and in the endoneurium. Electron-dense deposits, suggestive of immune complexes composed of hepatitis B virus, were demonstrated in the endoneurium of the patient with chronic relapsing polyneuropathy. These results suggest that HBsAg immune complexes may be of importance in the etiology of GBS or chronic relapsing polyneuropathy associated with hepatitis B virus infection.

The effects of pepsin on the natural progression of autoimmunity in glomerulonephritis in the NZB/W F 1 mouse

The effects of pepsin on autoimmune glomerulonephritis of New Zealand Black and White F 1 hybrid (NZB/W F 1) mice were investigated. Intravenous pepsin significantly improved survival rate and suppressed progressive increase in urinary protein and histopathological changes in kidney. Increased serum levels of immune complexes, anti-DNA antibody and natural thymocytotoxic autoantibody were decreased and abnormalities in lymphocyte subsets were ameliorated by pepsin. Pepsin suppressed autoantibody production and enhanced antibody production against xenogeneic substance in these mice. The fact that pepsin ameliorates abnormalities in immune function may contribute to the preventive effects of pepsin against pathogenesis and progression of immune complex nephritis.

On the mechanism of thrombocytopenic purpura in sexually active homosexual men.

Thrombocytopenic purpura has recently been noted in sexually active homosexual men. To elucidate the pathogenesis of thrombocytopenic purpura in this population, we compared the disorder in 33 homosexual men with that in 23 patients (15 women and 8 men) thought to have classic autoimmune thrombocytopenic purpura. The homosexual group had 3.8-fold higher levels of platelet-bound IgG and 4.2-fold higher levels of platelet-bound complement than the patients with autoimmune thrombocytopenic purpura. Eluates from the platelets of only 1 of 10 homosexual patients reacted in vitro with normal platelets, as compared with those from the platelets of 12 of 15 patients with autoimmune thrombocytopenic purpura. Twenty-one of 24 homosexual patients (88 per cent) had elevated serum levels of immune complexes that were capable of binding to platelets, whereas none of 5 patients with autoimmune thrombocytopenic purpura had circulating immune complexes. The IgG fraction of positive serum samples from three homosexual patients did not bind to normal platelets, whereas that from the positive serum of two patients with autoimmune thrombocytopenic purpura and one woman in whom isoimmune antiplatelet antibody developed during pregnancy (studied as a positive control) did bind to normal platelets. We conclude that, whereas classic autoimmune thrombocytopenic purpura involves antiplatelet IgG directed against platelet antigenic determinants, the thrombocytopenic purpura that occurs in sexually active homosexual men is usually caused not by antiplatelet IgG but probably by the nonspecific deposition of complement and immune complexes on platelets.

Immunologic enhancement of experimental metastasis in the rat.

Using a series of immunologically cross-reactive metastatic tumor variants, we demonstrate that serum from animals bearing pulmonary tumor colonies possesses enhancing properties in the experimental metastasis (lung colony) assay. Enhancement is produced by chronic serum administration and promotes the growth of tumor cells arrested in the lungs which would not otherwise proliferate to form grossly detectable lung nodules. Tumor-bearer serum from animals with lung colonies derived from the most highly metastatic variant examined is shown to possess enhancing properties in both BD-IX(H-1d) and BD-IV(H-1d) rat strains, while tumor-bearer serum from animals with lung colonies derived from the less metastatic parent tumor cell line possesses enhancing properties in the BD-IX rat strain only. Removal of immunoglobulin from enhancing serum by affinity column chromatography simultaneously removes the enhancing factor(s), and enhancing activity correlates with the presence of increased levels of Clq-binding immune complexes in the serum. Serum levels of immune complexes are shown to be more elevated in serum from animals bearing lung colonies derived from the most highly metastatic variant. The enhancing moieties are shown to bind to concanavalin A, but not to staphylococcal protein A, and the active fraction elutes from concanavalin A-Sepharose with alpha-methyl-mannoside. Consideration of immunoprecipitation studies on whole and fractionated enhancing sera, along with studies on affinity purified isotype fractions reveals that the activity resides with antibodies of IgG2b subclass.

Characterization of immune complexes in multiple sclerosis by an antigen-specific immune complex radioimmunoassay

Serum and cerebrospinal fluid samples from multiple sclerosis (MS) patients containing various levels of Clq-reactive immune complexes (IC) and samples from age- and sex-matched controls were tested by an antigen-specific IC radioimmunoassay which detects IC containing myelin membrane-related antigens. Positive reactivity in the assay was significantly associated with IC-containing MS sera ( P < 0.005) but such an association was not observed with MS cerebrospinal fluid. Analysis of longitudinal specimens revealed that the levels of the antigen-specific serum IC fluctuated with time. Significant correlation between serum levels of Clq-reactive IC and serum levels of IC containing myelin membrane-related antigens was observed ( r = 0.62; P < 0.001). Sucrose gradient centrifugation of sera from 1 patient showed that the IC had a peak density of 1.075 g/ml, indicating the presence of lipid material. The results suggest that serum IC of MS patients frequently contain myelin membrane-related antigens and that these antigens may be lipids or lipid-associated.

Urinary excretion of albumin and beta-2-microglobulin, glomerular filtration rate and immune complexes in serum during infectious mononucleosis.

Immune complexes in serum, urinary excretion of albumin and beta-2-microglobulin were determined in patients with infectious mononucleosis, both during the acute stage of the disease and one month later. At the first examination immune complexes were detected in 8 out of 12 patients, using both the ClqBA and the PP-Lc methods, but had disappeared in all after one month. Urinary excretion was initially increased for albumin in one of 9 and for beta-2-microglobulin in 5 of 9 patients. A significant fall in excretion was noted for beta-2-microglobulin during the acute phase (0.486 to 0.190 ng/min (medians), p less than 0.01) whereas albumin excretion did not change significantly (9.0 to 4.0 micrograms/min). Excretions were normal in all patients after one month. The magnitude of proteinuria was not correlated to the serum level of immune complexes. Serum beta-2-microglobulin was initially increased in 8 of 9 patients, but normal after one month (3.8 to 2.2 mg/l, p less than 0.01). There was a significant correlation between levels of beta-2-microglobulin in serum and urine (rho = 0.833, n = 9, p less than 0.01). 51Cr-EDTA clearance was the same during the acute illness and one month later. It is concluded that the abnormalities in urinary protein excretion do not seem to be related to the presence of circulating immune complexes in infectious mononucleosis and that the elevated urinary beta-2-microglobulin excretion is most likely due to increase production.

A study of the role of immunological factors in the pathogenesis of the anaemia of acute malaria

Children with acute Plasmodium falciparum malaria and anaemia were investigated to see if immunological factors could be implicated in the pathogenesis of their anaemia. Direct Coombs tests using an anti-whole immunoglobulin antiserum were negative in all 12 children tested but two had positive tests with antisera to C3b and C3d. Low plasma levels of C3 and C4 were found but these were not significantly different from values found in a group of children with acute malaria who were not anaemic. Serum levels of immune complexes were normal at the time of their presentation at hospital with anaemia but were elevated one month later. Incubation of group O rhesusnegative red cells in a serum pool obtained from children with acute malaria and anaemia did not cause enhanced haemolysis or reduce their survival time on injection into mice. Splenic uptake of red cells was, however, significantly enhanced. We conclude that the anaemia of acute malaria is due mainly to destruction of red cells by malaria parasites and to enhanced erythrophagocytosis of normal cells.