Presence Of Circulating Immune Complexes Research Articles

Formation and Glomerular Deposition of Immune Complexes in Mice Administered Human Antibodies: Evaluation of Dose, Frequency, and Biomarkers.

Administration of human protein-based drugs to animals often leads to formation of antidrug antibodies (ADAs) that may form circulating immune complexes (CICs) with the dosed protein. Circulating immune complexes can activate and bind complement (cCICs), and if large amount of CICs or cCICs is formed, the clearance mechanism potentially becomes saturated, which can lead to immune complex (IC) deposition and inflammation. To obtain a better understanding of the underlying factors, including the relationship between different dose regimes on IC formation and deposition and identification of possible biomarkers of IC deposition and IC-related pathological changes in kidneys, BALB/c and C57BL/6J mice were administered with human anti-tumor necrosis factor α (aTNFα, adalimumab) or a humanized anti-TNP (aTNP) antibody for 13 weeks. Particularly, ADA, CIC, cCIC formation, IC deposition, and glomerulonephritis were observed in C57BL/6J administered with aTNFα, whereas the immunologic response was minor in BALB/c mice administered with aTNFα and in BALB/c and C57BL/6J mice administered aTNP. Changing dose levels or increasing dosing frequency of aTNFα on top of an already-established CIC and cCIC response did not lead to substantial changes in CIC, cCIC formation, or IC deposition. Finally, no association between the presence of CICs or cCIC in plasma and glomerular IC deposition and/or glomerulonephritis was observed.

Circulating immune complexes levels correlate with the progression of canine leishmaniosis in naturally infected dogs

Dogs are the main domestic reservoir of Leishmania infantum, and in cases of uncontrolled infection, a strong humoral immune response is elicited, which is inefficient against the parasites. Previous studies have suggested that an adequate antigen/antibody ratio, with a moderate prevalence of antigens with respect to the antibodies, could result in the formation of circulating immune complexes (CIC) in canine leishmaniosis (CanL). Deposition of these complexes in tissues has been associated with vasculitis, uveitis, arthritis, dermatitis and especially glomerulonephritis and renal failure. However, little is known about the relationship between the presence of CIC and disease progression. The aim of this study was to evaluate serum CIC level and its correlation with disease severity in infected dogs with different stages of disease and non-infected animals as a control. A total of 60 dogs were included in the study, classified according to the proposed LeishVet classification criteria: healthy non-infected (n = 13); healthy infected (n = 12); sick stage I (n = 9); sick stage II (n = 17); sick stage III (n = 8); and sick stage IV (n = 1). CIC were isolated from serum samples using a modified polyethylene glycol precipitation method, and their levels measured by ELISA and bicinchoninic acid protein assay. A nanoparticle tracking analysis was performed to investigate the relationship between the molecular size distribution of the CIC and disease progression. In conclusion, the results confirmed a positive association between CIC levels, their molecular size and disease progression that suggests a potential use of CIC as biomarkers of CanL.

Formation and glomerular deposition of immune complexes in mice administered bovine serum albumin: Evaluation of dose, frequency, and biomarkers

In preclinical toxicity studies, species-foreign proteins administered to animals frequently leads to formation of anti-drug antibodies (ADA). Such antibodies may form circulating immune complexes (CIC) with the administered protein. These CIC can activate the classical complement pathway, thereby forming complement-bound CIC (cCIC); if large of amounts of CIC or cCIC is formed, the clearance mechanism may become saturated which potentially leads to vascular immune complex (IC) deposition and inflammation. Limited information is available on the effect of different treatment related procedures as well as biomarkers of IC-related vascular disease. In order to explore the effect of different dose regimens on IC formation and deposition, and identification of possible biomarkers of IC deposition and IC-related pathological changes, C57BL/6J and BALB/c mice were dosed subcutaneously twice weekly with bovine serum albumin (BSA) for 13 weeks without adjuvant. After 6 and 13 weeks, CIC and cCIC were detected in plasma; after 13 weeks, IC deposition was detected in kidney glomeruli. In particular immunohistochemistry double-staining was shown to be useful for detection of IC deposition. Increasing dosing frequency or changing BSA dose level on top of an already established CIC and cCIC response did not cause changes in IC deposition, but CIC and cCIC concentrations tended to decrease with increased dose level, and increased cCIC formation was observed after more frequent dosing. The presence of CIC in plasma was associated with glomerular IC deposits in the dose regimen study; however, the use of CIC or cCIC as potential biomarkers for IC deposition and IC-related pathological changes, needs to be explored further.

Human leukocyte antigen (HLA) associations, antibody titers and circulating immune complexes in patients with cystic echinococcosis

AbstractCystic echinococcosis (CE), caused by the parasite Echinococcus granulosus, is a prominent disease in Lebanon. The objectives of this study were to determine HLA allele-CE association in patients, and relate its presence to high anti-Echinococcus antibody titers and the presence of circulating immune complexes (CIC). Thirty patients and 20 controls were included. HLA profiles were determined by DNA-SSP typing. Relative risk and P-values were determined for each allele using Statcalc (EpiInfo, Version 6). Linkage disequilibrium was determined for associated alleles using SPSS 12.0 for Windows. Antibody titers were determined by indirect hemagglutination (IHA) and CIC by polyethylene glycol (PEG) precipitation. HLA-B*14 and HLA-DRB1*01 appeared to associate with protection against CE (P1 = P2 = 0.007 and P1 = P2 = 0.0007, respectively). However, it appeared that linkage disequilibrium did not exist between these 2 alleles (P = 0.250). HLA-B*35 was found to associate with susceptibility to disease (RR = 1.70, P = 0.02). Twenty five patients had anti-Echinococcus antibodies and 9 patients had CICs. However, there did not appear to be a correlation between the presence of HLA-B*35 and high antibody titers, or the presence of CICs. In conclusion, 2 HLA alleles that associate with resistance and 1 that associates with susceptibility to E. granulosus infection have been identified. The joint pain reported by some of the patients might be attributed to CIC deposits.

Circulating immune complexes in sera from patients with Alzheimer's disease and subjects with age-associated memory impairment.

Before, we reported a higher frequency of circulating immune complexes (CIC) in the sera from institutionalized Alzheimer's disease (AD), multi-infarct dementia and Down's syndrome patients than from age-matched controls. In this study, we tested the presence of CIC in the sera from an extended series of hospitalized AD patients, AD patients living in the community, from age-associated memory impairment (AAMI) subjects as well as from nursing home and community controls. We used two methods to measure CIC, C1q binding Elisa (C1qB-Elisa) and conglutinin binding (KgB-Elisa). The AD patients showed the highest frequency of positive findings and differed from the controls in KgB (42% vs. 17%) (Chi-square, p = 0.01) and C1qB (30% vs. 11%) (p < 0.05). In severe AD, 14/19 patients were KgB positive and 11/19 were C1qB positive and differed from controls. The frequency of CIC for the patients with moderate or mild dementia, the AAMI subjects and controls was similar. In the multivariate linear regression analysis, high CIC values of the AD patients significantly associated with a long disease duration and a history of recurrent urinary infections but not with age, sex, hospitalization, or the Mini-Mental Status score. We conclude that AD patients with severe dementia frequently show CIC but those with mild or moderate disease do not. The CIC relate to a long disease duration and a history of recurrent urinary infections.

Circulating immune complexes in renal injury.

T HE IMMUNOLOGIC basis of most forms of glomerulonephritis (GN) is well established. Immune-mediated glomerulonephritis in humans was initially defined by the pattern of glomerular immune deposits observed by immunofluorescence microscopy. Linear immunoglobulin (1g)G deposits along the glomerular basement membrane (GBM) were thought to be and have since been proven to be the result of antibodies binding directly to intrinsic renal antigens. In contrast, granular immune deposits were thought to result from passive trapping of circulating immune complexes (CIC). Following considerable controversy, it is now well established that granular immune deposits can arise from several mechanisms. In some cases, like anti-GBM disease, antibodies bind directly to intrinsic renal antigens; however, when the antigen is discontinuously distributed in the glomerulus, granular rather than linear deposits result. This is one form of in situ immune complex (IC) formation. Alternatively, granular immune deposits can be composed primarily of nonrenal antigens and their antibodies and reflect the formation of antigen-antibody (immune) complexes in the circulation and their localization within renal structures. The dynamics of formation of these complexes in the circulation, their trapping, rearrangement, and further accretion within the glomerulus, and the immunochemical characteristics that determine their ability to initiate renal injury are the focus of this article. The considerable progress that has been made in the previous 40 years in our understanding of immunecomplex mediated glomerulonephritis (ICGN) has been extensively reviewed previously and the reader is referred to those reviews for additional background. ‘-I2 The pathogenic potential of nonrenal circulating antigens is dependent on unique biochemical characteristics of the antigen as well as the nature of the immune response elicited by the antigen. Glomerular properties such as the high rate of blood flow, transcapillary hydraulic pressure gradient, fixed-negative charges within the capillary wall, and the unique set of extracellular matrix and cell surface proteins all contribute to the potential for macromolecular interactions that facilitate glomerular IC accumulation. The efficiency of the mononuclear phagocyte system for clearance of CIC is critically important, because glomerular IC accumulation increases when phagocyte function is impaired or overwhelmed.3~‘3~‘4 The dynamic equilibrium that exists between IC formation, clearance, and tissue accumulation is further illustrated in Fig 1 and discussed below. Despite our considerable knowledge, many questions remain unanswered. Early studies2*‘4-16 focused on quantitation of CIC as correlates of disease activity. These studies found the presence of CIC in the absence of disease manifestations and suggested that only subsets of IC were pathogenic. It was initially thought that CIC analysis would lead to antigen identification in human ICGN and thereby elucidate the etiologic agent and lead to an obvious approach to prevention and treatment. Early studies of serum sickness in the rabbit shed light on why our original hopes have not been fulfilled. Rabbits given identical antigen with identical dosage schedules develop a wide variety of histological forms and variable severity of ICGN. This indicated the critical importance of the individual animal’s immune response to the ultimate development of renal disease. Most current attempts to understand the pathogenic mechanisms responsible for ICGN are focused on basic concepts of regulation of the immune response and the unique biochemical characteristics of IC and their constituents that convey the capacity to deposit in the kidney (nephrotropic) and initiate injury (nephritogenic). In light of this, the antigen features that dictate antibody specificity, regulation of antibody synthesis, and the structure,

Treponemicidal activity of anti-treponemal lymphotoxins and their relation to circulating immune complexes and autolymphocytotoxins.

It was previously reported that spleen cells of rabbits infected with Treponema pallidum produced anti-treponemal lymphotoxins (ATL). This ability was distinctly disturbed when circulating immune complexes (CIC) and autolymphocytotoxins (AL) were present in the sera of cell donors. ATL liberated from cells of donors without CIC and AL displayed a marked ability to immobilize treponemes. The percentage of immobilized treponemes varied according to the type of cells used for ATL liberation and their density. The most active was ATL from T cells (density 4 x 10(8) ml-1) and the weakest was the one from B lymphocytes. In the presence of CIC in sera of cell donors the weakest ATL was from macrophages and in the presence of AL from T lymphocytes. When both factors (CIC and AL) were present ATL from T lymphocytes did not immobilize treponemes. This seems to suggest that the impairment of the cells' ability to produce ATL may facilitate the survival of treponemes in the host despite the presence of immunologically competent cells.

Treponemicidal activity of anti-treponemal lymphotoxins and their relation to circulating immune complexes and autolymphocytotoxins

It was previously reported that spleen cells of rabbits infected with Treponema pallidum produced anti-treponemal lymphotoxins (ATL). This ability was distinctly disturbed when circulating immune complexes (CIC) and autolymphocytotoxins (AL) were present in the sera of cell donors. ATL liberated from cells of donors without CIC and AL displayed a marked ability to immobilize treponemes. The percentage of immobilized treponemes varied according to the type of cells used for ATL liberation and their density. The most active was ATL from T cells (density 4 × 10 8 ml −1) and the weakest was the one from B lymphocytes. In the presence of CIC in sera of cell donors the weakest ATL was from macrophages and in the presence of AL from T lymphocytes. When both factors (CIC and AL) were present ATL from T lymphocytes did not immobilize treponemes. This seems to suggest that the impairment of the cells' ability to produce ATL may facilitate the survival of treponemes in the host despite the presence of immunologically competent cells.

Circulating immune complexes in sarcoidosis, a clinical role for the Raji assay?

Many immunological abnormalities, including circulating immune complexes (CICs), have been described in patients with sarcoidosis. The relationship of these abnormalities to clinical states is uncertain. In 31 proven cases of sarcoidosis we used the Raji assay in the investigation of the relationship between disease activity and the presence of CICs. Circulating immune complexes (greater than 49 micrograms.ml-1) were found in 11 of 14 patients with evidence of recent significant disease deterioration, whereas only one of 17 patients with chronic stable sarcoidosis demonstrated CICs (p less than 0.001). At follow-up, it was found that eight of the 11 cases with active disease and detectable CICs had resolved clinically. Resolution was accompanied by normalization of CICs in seven and persistence in one. The remaining three patients did not improve clinically and continued to demonstrate CICs. Measurements of complement levels did not demonstrate any significant difference between the two groups of patients. It is concluded that elevated levels of CICs, as detected by the Raji assay, are commonly found in association with significantly deteriorating sarcoidosis, often normalize following disease improvement and, consequently, may have a useful clinical role as a marker of activity.

Circulating immune complexes in tuberculosis — an indicator of activity

Circulating immune complexes (CIC) were assayed in 100 cases of tuberculosis and 30 age matched control children. The estimation was done by PEG assay before the commencement of antitubercular therapy. CIC were present in only 3.3% of the control children as compared to 68% of children with tuberculosis. The presence of CIC was observed to vary with the type of tuberculosis. The percentage positivity was highest (100%) in children with miliary tuberculosis. Subsequent estimation of CIC done after one and three months of antitubercular therapy showed a marked decrease in the percentage of positive cases (6.1 and zero percent respectively).

Radiological Changes and Circulating Immune Complexes in Patients with Urinary Schistosomiasis

The degree of infection and the urographic picture was correlated to the presence and level of circulating immune complexes (CICs) in 69 patients affected by urinary schistosomiasis. Patients were divided into 2 groups: those eliminating less and those eliminating more than 25 eggs/10 ml of urine. Radiological changes in the urinary tract were present in 67% of patients, the most frequent finding being single or multiple filling defects in the bladder. CICs were present in 39 patients. A positive correlation was found between the presence and level of CICs and the output of Schistosoma haematobium eggs, as well as between the presence of CIC and single or multiple filling defects of the bladder. Our findings indicated that CICs were present in patients with urinary schistosomiasis, but the different incidence in patients with a large egg output and radiological filling defects suggests a possible pathogenic role only in the earlier phase of the infection.

Study of circulating immune complexes during the evolution of visceral Mediterranean leishmaniasis

In the present study, sera of 56 children suffering from visceral Mediterranean leishmaniasis were analysed. The incidence of circulating immune complexes (CIC) by ELISA technique using the conglutinin binding assay was 39% before treatment, 28% after the first treatment, and nil at the end of the second one. The C4 levels remain low even after treatment. The anti-leishmania antibodies (AAL) account for 95% of the cases before treatment and 84% after treatment. The rheumatoid factor (FR) also remains with more or less the same frequency (74%) before and after treatment. The search for a correlation between the presence of CIC and the other immunological factors show that the average titre of AAL is higher in the group of patients that have CIC than in the group that does not. The C4 levels are significantly reduced in the CIC positive group of patients, whereas the rate of IgG is significantly increased in the same group. The study of the evolution of CIC under treatment in nine patients shows that they disappear at the end of the treatment, and that the FR reduces but does not disappear.

Effect of factors inhibiting HLA-DR antibodies before transplantation on kidney graft survival.

Blood transfusions administered before renal allografts are known to enhance graft survival. Among alternative hypotheses proposed to explain this effect, one of the most attractive is the possible induction of antiidiotypic antibodies directed against the specific antigen-binding site of donor-specific antibodies. In order to determine if such blocking antibodies are generated after blood transfusions, serial serum samples obtained before transplantation from 44 kidney recipients were analyzed for the development of HLA-DR alloantisera inhibitory activity by a microcytotoxicity inhibition assay. A significant correlation was found between the presence of inhibitory factors before transplantation and prolonged graft survival. However a clear relation between the development of inhibitory factors and the administration of transfusions could not be established. In addition the sera of 36 patients were studied for the presence of circulating immune complexes (CIC) before grafting. The presence of CIC was clearly associated with that of inhibitory factors, and with a prolonged graft survival. Thus these studies provide support for the development of blocking (possibly antiidiotypic) antibodies to anti-MHC in human renal graft recipients.

Lack of effect of gamma-globulin infusion on circulating immune complexes in patients with Kawasaki syndrome

Previous studies have demonstrated circulating immune complexes (CICs) in sera of 70% of Kawasaki syndrome (KS) patients but the pathogenic role of these complexes in the illness is unknown. Infusions of gamma-globulin (GG) have been shown recently to reduce the prevalence of coronary artery aneurysms in KS patients. One of the proposed mechanisms of action of GG therapy is through an effect on CICs. We analyzed paired sera for CICs from 29 patients with KS, 19 of whom were treated with aspirin and GG and 10 of whom received aspirin only. Assay systems used for CIC detection were Raji-mu enzyme immunoassay, C1q solid phase assay-enzyme immunoassay and F(ab')2-anti-C3-mu enzyme immunoassay. Overall 20 of 29 patients had CICs detected by at least two of three assays used. Of the 19 GG-treated patients 14 had CICs detected: 5 in both paired sera; 2 in pretherapy sera; and 7 posttherapy specimens. There was no correlation between duration of fever, presence of myocarditis or the development of coronary artery aneurysms and the presence of CICs in the serum of KS patients. Although CICs can be found frequently in the sera of KS patients there seems to be no association between the presence of CICs and the duration of fever or the development of coronary artery aneurysms.

Characterization of specific immune complexes in HIV-related disorders.

Eighty-seven seropositive subjects with HIV (human immunodeficiency virus) infection together with 20 normal controls with no history of any illness were investigated for the presence of circulating immune complexes (CIC) by the conglutinin binding assay (KgBA) and further studied for isotype characterization of CIC. Six out of 87 patients showing very high values for immune complexes (CIC) were studied for the presence of free antigen. In 3 out of 6 (1, IVc1; 1, III; 1, IVa) we could detect by ultracentrifugation analysis the presence of specific HIV (p15) anti-HIV (anti-p15) and gp41-anti-gp41 CIC. Evidence in favour of this finding is supported by: the presence of specific CIC (p15-anti-p15 or gp41-anti-gp41) seen only at pH 7.2; the apparent presence of free antigen and specific HIV antibodies were only at pH 4.0. The relevance of this finding lies in the attempt to explain the occurrence of false seronegativity seen occasionally in symptomatic patients. Thus, the presence of CIC might perhaps interfere in the routine assay (i.e. ELISA) making the diagnosis difficult. All these considerations will have to be taken into account in the future handling of this disease.

Immune complexes and complement activation following rupture of intracranial saccular aneurysms.

Circulating immune complexes (CIC) and complement activation (plasma C3d levels) were monitored during a 2-week period in patients with ruptured cerebral aneurysms and also in patients with cerebral hematoma unrelated to saccular aneurysms. Thirteen of 18 aneurysm patients were found to have CIC on admission as compared to three of 21 healthy blood donors (p less than 0.001). The presence of CIC in aneurysm patients was associated with a poor prognosis. Eight of nine patients who developed angiographic vasospasm had CIC on admission compared with one of four without vasospasm. Patients with vasospasm showed a twofold increase in plasma C3d levels at the time when the spasm occurred, whereas no significant changes in the C3d concentration could be demonstrated in aneurysm patients without spasm or in patients with hematoma unrelated to aneurysm rupture. These findings suggest that immunological processes involving complement-activating immune complexes are involved in the pathogenesis of cerebral vasospasm following rupture of saccular aneurysms.

Altered erythrocyte C3b receptor expression, immune complexes, and complement activation in homosexual men in varying risk groups for acquired immune deficiency syndrome.

We studied levels of erythrocyte C3b receptors (E-CR1) and correlated them to the level of circulating immune complexes (CIC) and complement activation in patients with or at risk for acquired immunodeficiency syndrome (AIDS). A significant reduction was found in patients with AIDS (185 +/- 93 CR1/cell), AIDS-related complex, and generalized lymphadenopathy, whereas healthy male homosexuals or normal controls had 434 +/- 193 and 509 +/- 140 CR1/cell, respectively (P less than 0.001). Family studies indicate that this defect is acquired. Reduction in E-CR1 was associated with increased levels of CIC when assayed by binding to Raji cells, but not when tested by C1q binding. Complement activation was assessed by levels of C3bi/C3d-g in plasma, measured with a monoclonal antibody specific for a neoantigen in C3d. AIDS patients had increased C3 activation (2.68 +/- 1.67%) when compared with normal controls (0.9 +/- 0.22%) (P less than 0.01). The decreased E-CR1, the presence of CIC, and C3 activation suggest that complement activation by immune complexes may play a role in the clinical expression of the disease.

Enhancement of Circulating Immune Complexes in Episodic Cluster Headache

Abnormalities have already been reported in the phenotypic frequency of the major histocompatibility complex antigens and in the relative proportions of the leukocyte subsets in patients affected by episodic cluster headache (ECH). Circulating immune complexes (CIC) and leukocyte subsets have been studied in 19 patients affected by episodic cluster headache during and in the absence of periods of crisis. The presence of CIC was determined in another five patients outside periods of crisis. CIC were evaluated using two techniques based on different principles revealing different types of CIC: the solid phase Clq method, and the conglutinin radioimmune assay. Monoclonal antibodies have been used to phenotype total T, helper/suppressor, K and NK leukocyte subsets, and monocytes. The findings demonstrate an increased incidence of CIC in the 19 ECH patients followed with time (37%) with respect to control subjects (10%), and an increase in Leu7-positive cells (K and NK cells) and in LeuM3-positive cells (monocytes). Interestingly, when patients were grouped according to the presence of CIC, only CIC-positive patients showed the previously described abnormalities. This would suggest that the cell-mediated immune alterations present in these patients may interact with the presence of CIC.

Correlation of disease activity with circulating immune complexes (C1qbA) and complement breakdown products (C3D) in patients with systemic lupus erythematosus. A prospective study.

Most biologic effects of immune complexes are mediated through the activation of the complement system. The relationship between lupus disease activity and the presence of C3 breakdown products (C3d) and circulating immune complexes (CIC) as demonstrated with the C1q binding assay (C1qbA), was evaluated. Nearly all 13 systemic lupus erythematosus (SLE) patients had a stable disease course in this prospective study, nevertheless, in each patient the profiles of the serologic parameters were quite different. Despite the small number of investigated patients (13), it is concluded that irrespective of the disease activity, the serologic parameters could be either positive or negative. No relationship could be obtained between disease activity and the presence of C3d and/or CIC. Nor was there any evidence that the presence of CIC would indicate increased levels of C3 breakdown products (C3d). This observation argues against a pathogenetic significance of CIC detected by the C1qbA in SLE. In conclusion, the supposed link between the presence of CIC, consumption and activation of the complement system, and the activity of SLE needs further study.

Circulating immune complexes in Fièvre boutonneuse.

Circulating immune complexes (CIC) occurred in 36% of a group of 25 patients with Fièvre boutonneuse. CIC were present only in the first week of the disease and there was no evidence of other humoral immunological abnormalities or alterations of the coagulation factors studied. The presence of CIC was not associated with a more severe clinical manifestation or with symptoms or tissue injuries. It is considered that CIC do not play a major role in Fièvre boutonneuse.