C1q Binding Assay Research Articles

Immune complexes in patients with contact dermatitis.

By C1q binding assay, circulating immune complexes (cic) were detected in 19 out of 30 patients with contact dermatitis to nickel or chromium. Their presence was correlated with the duration of the disease, while any patients positive for cic showed any signs of type III immunopathological lesions. Atomic absorption analysis of the polyethlylene glycol precipitates (PEG ppt) from the sera of 16 patients--8 positive and 8 negative for cic--revealed an amount of nickel or chromium significantly higher in the PEG ppt from the sera of patients positive for cic.

In vivo Reduction of Circulating C1q Binding Immune Complexes by Intravenous Gammaglobulin Administration

Six patients with systemic lupus erythematosus were treated with high-dose intravenous gammaglobulin. Immunological parameters were studied and included solid-phase immune complex determinations, quantitative immunoglobulins G, A, and M, as well as C3 and C4 concentrations. Pretreatment values of circulating immune complex concentrations as measured by either C1q binding or anti-C3 binding assays were elevated in all patients. Posttreatment values showed reductions in all C1q binding immune complexes (p less than 0.01) and anti-C3 binding immune complexes also decreased in 5 out of 6 patients. These assays are described in detail and were also used to define in vitro interactions between the intravenous gammaglobulin preparation and heat-aggregated IgG or sera containing elevated circulating immune complexes. No reduction of immune complex levels were observed when IgG was incubated in vitro with either heat-aggregated IgG or sera with elevated immune complex concentrations. The duration of the in vivo effect and the patients' clinical responses are described. These findings show that high-dose intravenous gammaglobulin administration can reduce certain types of immune complexes in patients with elevated levels of these substances.

Multiple sclerosis. Cerebrospinal fluid immune complexes that bind C1q.

We used a sensitive C1q-binding assay to measure levels of soluble immune complexes in 182 samples of cerebrospinal fluid (CSF) from control patients and patients with multiple sclerosis (MS). Soluble immune complexes in CSF were detected in 16% of patients with progressive MS, 38% of patients with exacerbating-remitting MS, 55% of patients with infectious or inflammatory diseases, 3% of patients with noninflammatory neurologic disorders, and in 0% of control patients with back pain. No correlations were found between the results of the C1q-binding assay and abnormalities of other CSF parameters. These included an elevated level of myelin basic protein, pleocytosis, oligoclonal bands, or an increased IgG level. Because of the lack of correlation to laboratory indexes of disease activity and the nonspecificity of a positive test, the C1q-binding assay seems to have little clinical usefulness in the diagnosis or management of patients with MS.

Evaluation of circulating immune complexes in lymphomas and leukemias using two different assays.

Circulating immune complexes (CICs) have been detected in the sera of patients with non-Hodgkin's lymphoma (NHL), Hodgkin's disease, chronic myeloid leukemia, and acute lymphoblastic leukemia by using C1q-binding and L1210-binding assays. Both assays gave broadly similar patterns of reactivity in terms of frequency and magnitude, though there are some differences. Significantly elevated CIC levels were observed in all pathologic groups. However, sera from NHL patients with an unfavorable prognosis consistently exhibited the highest frequency of positive values and mean CIC levels in both these assays. The two tests showed concordance in 66.6% of the NHL patients' sera and were significantly correlated. Of the sera from NHL patients 12.7% were positive in the C1q-binding assay only and 15.9% in the L1210-binding assay only. Both the assays gave positive results in some patients, and a degree of overlap indicates the presence of different types of CIC in cancer patients' sera. The combined use of two methods for detecting CICs may be useful for evaluation of the activity, the extent, and the prognosis of the malignant disease.

The value of complement and immune complex determinations in monitoring disease activity in patients with systemic lupus erythematosus.

Serial serum samples from 33 patients with systemic lupus erythematosus were tested for CH50, C3, C4, and circulating immune complexes. Circulating immune complexes were determined by 5 different assays. Disease activity was determined by a scoring system we devised. On an interpatient analysis, overall disease activity correlated significantly with levels of CH50, C3, and a positive result on C1q binding assay. However, with the exception of depressed C3 levels, the sensitivity, specificity, and predictive values of all the serologic tests were low. An intrapatient analysis revealed a patient-specific activity parameter in 11 of the 33 patients. We conclude that these serologic tests are not reliable in assessing disease activity in patients with systemic lupus erythematosus, although a small subgroup of patients will exhibit a patient-specific activity parameter.

Clinical importance of circulating immune complexes in human acute lymphoblastic leukemia.

A total of 122 sera from acute lymphoblastic leukemia (ALL) patients were analyzed for circulating immune complexes (CIC) by two methods: the 125I-Clq binding assay and the polyethylene glycol precipitation test (PEG). The results were correlated with induction, remission and relapse stages of the disease. Using the first method the levels of CIC in induction were 15.18 +/- 9.15, with 19/29 positive cases (65.50%), P less than 0.001 compared with controls. In the remission phase the levels were 9.02 +/- 5.62, 11/45 (24.49%) nonsignificant P value, and in relapse they were 16.14 +/- 11.17 28/48 (58.33%) P less than 0.001. The PEG precipitation test results were: 0.33 +/- 0.10, 8/22 (36.36%); 0.24 +/- 0.11, 10/48 (20.83%) and 0.28 +/- 0.10, 6/28 (21.42%), respectively. Thus the values of CIC as measured by PEG in the three clinical of phases ALL did not differ significantly from controls. This contrasts with results obtained by the radioiodinated C1q binding assay, where the incidence of positive values was significantly higher in induction and in relapse and lower in the remission phase. These observations were extended in sequential vertical studies performed in a group of patients. These results suggest that raised CIC detected by the 125I-C1q method may reflect a progressive state in ALL and that quantitation of these immune complexes may provide an adequate biochemical marker for prognosis.

Reduced opsonisation of protein A containing Staphylococcus aureus in sera with cryoglobulins from patients with active systemic lupus erythematosus.

Among a total of 41 patients with systemic lupus erythematosus (SLE) 11 of 14 patients with active disease had reduced capacity (p less than 0.05) to opsonify Staphylococcus aureus in undiluted sera, as compared with nine of 27 patients with inactive disease (p less than 0.02). The opsonic reduction in the active patients increased with the number of active organ systems (p less than 0.002). No correlation was found between reduced opsonisation and corticosteroid treatment, or serum concentrations of complement components (C) of the classical pathway, or bacteria-associated activated C3. When the cryoglobulin fraction of immune complexes (IC) was removed, normal opsonic capacity was restored, and the opsonic reduction could be transferred with the cryoglobulins to pooled serum. Increased IC values, as measured by C1q binding assay, were found in conjunction with reduced opsonic capacity (p less than 0.04). Since opsonisation in SLE sera of a protein A deficient strain of S. aureus was normal, reduced S. aureus phagocytosis in SLE sera may be explained by IC binding to staphylococcal protein A.

Humoral immunity in normal and complicated pregnancy

To evaluate the role of some immunological phenomena involved in the pathogenesis of preeclamptic toxaemia, we studied the humoral immune reactivity in patients with preeclamptic toxaemia during the third trimester of pregnancy, and three days and six weeks after delivery. The results were compared with those of patients with intrauterine growth retardation and with uneventful pregnancy. During the third trimester, patients with complicated preeclamptic toxaemia had significantly lower IgG, CH50, C4 and C3 levels than normal pregnants. Post-partum levels of IgM were significantly higher than in all other groups of patients. Circulating immune complexes were not detectable by a C1q binding assay in patients and controls. However, with a conglutinin binding assay and a granulocyte phagocytosis test complexes were demonstrable in patients with complicated preeclampsia (incidence 44% and 33%, respectively). In addition, 66% of these patients showed deposits of immunoglobulins and complement components in superficial blood vessels of the skin biopsy, suggestive of the presence of tissue deposits of immune complexes. This was found in about 30% of the other patient groups and in none of control pregnants. Allo-antibodies to lymphocytes were present in 63% of complicated preeclamptic toxaemia patients and 22% of normal pregnants. Our data show several changes in humoral immune reactivity in preeclamptic toxaemia which may contribute to the pathogenesis of this disorder.

Ability to activate complement is not required for the detection of immune complexes by the fluid-phase C1q binding assay.

Ability to activate complement is not required for the detection of immune complexes by the fluid-phase C1q binding assay.

Does Fibronect in Influence the Determination of Circulating Immune Complexes by Means of a Clq-Enzyme Immunoassay?

Abstract Fibronect in was shown to bind to solid-phase C1q and to inhibit the binding of aggregated lgG in an C1q-solid-phase enzyme immunoassay in the absence of human serum. In the presence of human serum the determination of aggregated lgG and circulating immune complexes is not influenced by fibronectin in this assay. Therefore, we suggest that fibronectin does not affect the determination of immune complexes in serum specimens by C1q binding assays.

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.

A new enzyme-linked immunosorbent assay (ELISA) for measuring immunoconglutinins directed against the third component of human complement. Findings in systemic lupus erythematosus

A new enzyme-linked immunosorbent assay, using purified activation product of the third component of human complement (C3b), detects immunoglobulins of the IgG isotype which demonstrate affinity for C3b (C3b-immunoconglutinins; C3b-IK). This assay offers significantly improved specificity compared to previous immunoconglutinin (IK) assays in that it not only defines the isotype and antigenic specificity of the IK but also eliminates false positive results associated with immune complexes or aggregated human gamma globulin, or with natural antibodies directed at heterologous reagents. Using this assay, we observed elevated C3b-IK levels in serum of 34 systemic lupus erythematosus (SLE) patients when compared to serum of 13 healthy controls. Comparing sera from patients with clinically active and clinically inactive lupus showed greater immunoconglutinin levels in the active group. Immunoconglutinin levels did not correlate with the erythrocyte sedimentation rate, total hemolytic complement, or with circulating immune complex levels by the Raji cell and C1q-binding assays.

A re-examination of the incidence of circulating immune complexes in normal pregnancy.

Circulating immune complexes were detected in 20% of serum samples from pregnant patients by the liquid-phase C1q-binding assay. Two other immune complex assays yielded negative results with the same samples. A careful case study was also carried out in which serum samples from before, during and after a normal pregnancy were analysed. The results are discussed in relation to the contradictory data previously published in this field.

C1q binding and C1q deviation assays using enzyme labelled C1q

Methods for the enzyme labelling of C1q are described. The C1q conjugates have been incorporated into suitably modified C1q deviation and C1q binding assays for circulating immune complexes. These assays show the expected high positivity rate in sera from patients with systemic lupus erythematosus. The assays using enzyme labelled C1q confer considerable advantages over their counterparts using 125I.

Serum immunoglobulin sedimentation patterns and circulating immune complexes in IgA glomerulonephritis and Schönlein-Henoch nephritis.

Sera from 8 patients with IgA glomerulonephritis and from 6 patients with Schönlein-Henoch nephritis were investigated by the C1q-binding assay (C1q-BA) test and by sucrose gradient centrifugation followed by sensitive solid phase radioimmunoassay determinations of IgA, IgG and IgM in each fraction obtained. Abnormal sedimentation profiles were found in sera from 3 of 8 patients with IgA nephritis and in 3 of 6 patients with Schönlein-Henoch nephritis. The abnormal fraction consisted of low molecular weight IgA in 2 patients, IgG in 1 patient and IgM in 4 patients. The absolute level of polymeric IgA was increased in 3 of 8 patients with IgA nephritis, but the relative distribution was normal. An abnormal sedimentation pattern of immunoglobulins was correlated to a positive C1q-BA test (p less than 0.001).

Circulating Immune Complexes in Regularly Dialyzed Patients with Chronic Renal Failure

The prevalence of circulating immune complexes (CIC) was investigated using the C1q binding assay (C1q BA) and the conglutinin binding assay (Kg BA) in 200 patients undergoing maintenance hemodialysis. Increased C1q binding was found in 45% (87 of 194) of the patients, and the modified Kg BA gave elevated values in 31% (20 of 65). The prevalence of CIC was similar in American and Swiss patients, and in patients undergoing hemodialysis, self-dialysis or peritoneal dialysis. In patients with 'nonimmunological' renal diseases, CIC were detected with similar frequency. No change in CIC was noted during hemodialysis in 6 additional patients tested. The abnormality was not related to age, sex, duration of dialysis, hepatitis B antigenemia, bacterial infections, or transfusions. Anti-DNA antibodies were absent in all subjects tested and the results of the C1q BA were not changed by DNase digestion of eight sera with high C1q binding. Rheumatoid factor activity (RF) was detected in approximately one-fifth of the patients, and there was a direct correlation between positive C1q binding and RF. There was no correlation between CIC and lymphocytotoxic antibodies. This study demonstrated a high prevalence of CIC in dialyzed uremic patients and established its relationship to other immunological abnormalities.

Evaluation of circulating immune complexes in lupus nephritis by solid phase C1q and conglutinin binding assays.

Evaluation of circulating immune complexes in lupus nephritis by solid phase C1q and conglutinin binding assays.

Association of C1q- and conglutinin-binding immune complexes with high consumption of alpha-2-macroglobulin in synovial fluids of patients with rheumatoid arthritis.

The consumption of alpha-2-macroglobulin (a2M) by proteinases in synovial fluids (SF) was indirectly measured by determining trypsin binding to solid-phase immunoadsorbed SF-a2M. In addition immune complexes (IC) were assessed by the solid-phase C1q-binding assay as well as the solid-phase conglutinin binding assay in rheumatoid (RA; n = 25) and osteoarthritic (OA; n = 9) SF. Elevated levels were found as follows: a2M X proteinase complexes (a2M X P) in 73.5% (RA, n = 20; OA, n = 5), solid-phase C1q-binding IC (C1q-IC) in 52% (13 out of 25 RA-SF) and bovine conglutinin binding IC (KgB-IC) in 54% (13 out of 24 RA-SF). All OA-SF were in either IC assay negative. Consumption of a2M in OA-SF and seronegative RA-SF was not more than 15% of total SF-a2M, showing a mean value of 19.5 and 13.5 micrograms a2M X P/ml SF. Seropositive RA-SF had an a2M X P mean value of 96.4 micrograms/ml SF, which differed significantly (p less than or equal to 0.05) from the former two groups. Similarly, RA-SF which were negative in either IC assay had a low a2M X P mean value (20.0 micrograms/ml SF). This contrasted sharply with the a2M X P means obtained in IC-positive RA-SF, which amounted to 131.5 micrograms a2M X P/ml SF in C1q-IC positive RA-SF and to 110.4 micrograms a2M X P/ml SF in KgB-IC positive RA-SF, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorbance nephelometry of C1q-precipitable immune complexes: method comparisons and clinical correlations.

Using a double-beam spectrophotometer, we investigated the clinical utility of a nephelometric method for assaying immune complexes. The complexes were concentrated from serum by precipitation with polyethylene glycol (PEG) and assayed by reaction with C1q. Testing of more than 100 sera showed a Spearman's rank correlation (p) between the present assay and the C1q-binding assay of 0.57, and 0.39 between the Raji cell assay and the present assay. Clinical sensitivity of the methods was not statistically different (p less than or equal to 0.5). Twenty-four of 30 patients with symptoms of disease showed increased concentrations of immune complexes by the present assay; only one of 38 normal individuals showed an increase. In a longitudinal study, we found that the concentrations of immune complexes paralleled clinical changes, indicating good clinical utility. The use of this assay with single-beam analyzers is limited because of the poor aqueous solubility of the PEG precipitate. Ongoing investigations designed to circumvent this problem are described.

Localised immune complexes and slipped upper femoral epiphysis.

Slipped upper femoral epiphysis remains a disease of unknown aetiology. Recent evidence has bolstered speculation that the immune system may play a role in the aetiology or pathogenesis of slipped epiphysis or of one of its complications, chondrolysis. This study reports the finding of immune complexes in the synovial fluid of all but one hip affected with slipped epiphysis in a consecutive series. In seven patients, immune complexes were detected by both the Raji cell assay and C1q-binding assay; in two, by the C1q-assay only; and in one, by the Raji cell assay only. No patients had immune complexes in the serum. Twenty-one patients with synovitis of the knee or hip caused by a variety of disorders served as the control group. Two of these patients had immune complexes in their synovial fluid. It appears that the immune complexes characterise the synovitis found with slipped upper femoral epiphysis as distinct from most other synovitides.