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PubMed1978

Studies on the occurrence of circulating immune complexes in vascular diseases.

The presence of circulating immune complexes was studied in 347 samples of serum from 212 patients with various vascular diseases. Two quantitative methods (complement-consumption assay and C1q-solubility test) were used for the measurement of the concentration of the complexes. Immune complexes were detected in each group of patients tested (coronary arteriosclerosis, myocardial infarction, cerebral artery sclerosis, arteriosclerosis obliterans, phlebothrombosis, pulmonary infarction). A high proportion of positivity was recorded in myocardial infarction (in 43 patients out of the 94 tested) and in arteriosclerosis obliterans (7 out of 11 cases). The possible pathogenic role of the circulating immune complexes is discussed.

Aged↗
PubMed1975

Anti-human C1q: rapid and simple method for preparing monospecific antisera.

A new simple, rapid and economical method is described for producing monospecific antisera to human C1q without using gel filtration or column chromatography. Moderately purified C1q is obtained by dialyzing fresh human serum in the presence of chelating agents at low ionic strength and then electrophoresing it in agarose. When injected into rabbits, the electrophoretically purified product induced potent antisera to three or four serum proteins including C1q, all with slow electrophoretic mobilities (gamma to beta) at pH 8.6. The antibodies to serum proteins other than C1q are easily removed by immunoadsorbents consisting of the insolubilized supernatants obtained from the dialysis used to make the original C1q-rich fraction. The monospecific antisera prepared by this technique form only one band of precipitate in the slow gamma region in immunoelectrophoresis with whole human serum or C1q-rich solution, as well as in Ouchterlony double diffusion test. They agglutinate EAClq but not EA cells and detect the same antigen as standard monospecific antisera to human C1q obtained by another well-established method.

Adsorption↗
PubMed1977

Quantitation of immune complexes by competitive inhibition of binding of Clq to insoluble IgG aggregates.

An assay system for the binding of Clq to insoluble IgG aggregates was found useful for the quantitation of immune complexes in biological fluids. The assay, both easily and rapidly performed, is based on the competition of Clq binding substances with IgG aggregates. Serum from rheumatoid arthritis patients showed an increase in Clq binding substances over normal serum and this increase could be abolished by pretreatment of the serum with D-penicillamine.

Antigen-Antibody Complex↗
PubMed1977

Detection of circulating immune complexes in human sera by simplified assays with polyethylene glycol.

The search for circulating immune complexes by precipitation tests using polyethylene glycol (PEG) was performed on a series of normal and pathological sera. Various factors affecting PEG precipitation were studied. Immunoglobulins and complement factors percipitated by PEG (3.5%) were quantified and their significance was discussed in relation to serum levels. The PEG test was compared to labeled C1q binding test with a fairly good correlation. The direct evaluation of the amount of C4 precipitated with IgG by 3% PEG (C4 test) provided a simpler routine assay than the C1q binding test for detecting complement-fixing immune complexes. The direct PEG test and the C4 tests gave positive results in patients with diseases generally presumed to be associated with immune complexes including systemic lupus erythematosus, acute glomerulonephritis, bacterial sub-acute endocarditis and chronic acitve hepatitis. The demonstration of HBs antigen and antibody after acid dissociation of PEG precipitates from hepatitis B seronegative sera illustrated the fact that PEG does precipitate and thus concentrates circulating immune complexes.

Adult↗
PubMed1978

Activation of the classical and alternative pathways of complement fixation by immune complexes containing normal and tryptophan-modified immunoglobulin G.

Koshland's reagent (2-hydroxy-5-nitrobenzyl bromide (NBB)) has been shown to modify tryptophanyl residues in anti-ovalbumin IgG. As little as 2 moles NBB/mole IgG antibody are sufficient to block the classical pathway of complement activation when the antibody is complexed to antigen (ovalbumin). In contrast, immune complexes containing antibody with the same degree of tryptophanyl substitution will activate the alternative pathway of complement fixation. Immune complexes containing F(ab')2 fragments derived from anti-ovalbumin IgG do not activate the classical pathway. When measuring the percentage activation of C3 using the method of Laurell, NBB does not affect the alternative pathway of the complement system up to a molar ratio of 2 NBB/F(ab')2. The above findings, provide a means to evaluate the relative contribution of complement activation by the different pathways.

Animals↗
PubMed1979

Aggregated human immunoglobulin G stabilized by albumin: a standard for immune complex detection.

Stabilized preparations of heat-aggregated human immunoglobulin G (A-IgG) of restricted size were made by separating A-IgG by sucrose density gradient ultracentrifugation in the presence of bovine serum albumin (BSA). Periodic recentrifugation of stored fractions of the radiolabelled A-IgG indicated that the initial sedimentation characteristics were preserved. Pooled fractions of A-IgG stored for up to 16 months had the same functional activity as freshly prepared A-IgG of corresponding size when assessed by activation of the first component of complement and consumption of C4 and CH50 in normal human serum. It was also found that the reactivity of A-IgG in the C1q binding assay (C1Q-BA) and the conglutinin binding assay (Con-BA) was not altered by long-term storage of these A-IgG. Testing different batches of [125I]C1q and conglutinin with the same batch of stabilized A-IgG showed variations due to the instability of both [125I]C1q and conglutinin. The influence of these variations on the quantification of the levels of immune complexes in sera was reduced by using stable A-IgG as a reference. The assays were compared to determine the effect of the size of the aggregate. The C1Q-BA detected preferentially A-IgG of large size, while size had no influence in the Con-BA. These results suggest that the stability of A-IgG in BSA is such that this preparation may be used as a reliable standard for immune complex assays.

Animals↗
PubMed1980

Measurement of antigen-antibody complexes in mouse sera by conglutinin, C1q and rheumatoid factor solid phase binding assays.

The application of three solid phase tests for the detection of antigen-antibody complexes in the sera of inbred and selectively-bred mice with experimentally induced chronic antigen-antibody complex disease is described. Two of the tests used--the C1q binding assay (C1qBA) and the conglutinin binding assay (KBA)--were previously described methods which we have modified for the detection of murine complexes. The third test is a new solid phase polyclonal rheumatoid factor binding assay (RFBA). The results demonstrate that the correlation of positivity with the three methods varied during the course of a chronic disease but in general results with the KBA showed a better correlation with the RFBA than with the C1qBA. Furthermore, the KBA and RFBA preferentially bound complexes of lower molecular weight than did the C1qBA. It is suggested that the parallel use of these three tests during the study of murine antigen-antibody complex disease will provide valuable information concerning the nature of the complexes involved; since the three tests, when run in parallel, will detect large complement fixing complexes (C1q), small complement fixing complexes (KBA) and small non-complement fixing complexes (RFBA).

Animals↗
PubMed1980

A simple immunofluorescence assay for C1q binding.

Antibody-independent binding of B1q to Crithidia luciliae kinetoplast DNA was demonstrated by immunofluorescence microscopy. The method allows detection of C1q in human sera diluted 1/20--1/40 and in 5--10 micrograms/ml concentrations of isolated C1q. Various substances known to interfere with the early events of complement activation inhibited binding of C1q to kinetoplasts. The method may be used as a functional assay for serum C1q.

Binding Sites, Antibody↗
PubMed1980

A simplified method for the preparation of EAC14.

Sheep erythrocytes (E), sensitized with unheated rabbit antiserum containing IgG antibodies (EA), bound human C4 when heat-inactivated serum was used as the source of complement (EAC). The EA were not agglutinated by antiserum to rabbit C3 and were not lysed in the presence of C4-deficient guinea pig serum. The EAC were agglutinated by antiserum to human C4, lysed by the addition of C4-deficient serum and were reactive in immune adherence. They were not agglutinated by antiserum to human C3. Accordingly, the cells could be designated as EAC14. They were stable and could be stored at 4 degrees C for at least 1 week without haemolysis occurring, and with no loss of reactivity in immune adherence test. E sensitized in the presence of EDTA or with heat-inactivated rabbit serum did not bind C4.

Animals↗
PubMed1980

Analysis of the different types of leukocyte membrane complement receptors and their interaction with the complement system.

The specificity, distribution, and structure of 8 different types of leukocytes membrane complement (C) receptors (CR1, CR2, CR3, and receptors for C1q, beta 1H, C3e, C3a, and C5a) are discussed. Recent data are reviewed on the synthesis of C components by macrophages and B lymphocytes, and how these components may function in the activation of these two cell type by the C system. Commonly used C receptor assay procedures are evaluated in terms of both specificity and sensitivity. Specific assay procedures are recommended for measuring CR1 (C4b-C3b receptor), CR2 (C3d receptor), CR3 (C3bi receptor), and the beta 1H receptor. Assays include both rosette and fluorescence procedures for detection of C receptors on either mouse or human leukocytes. Primary systems have been selected for optimal sensitivity and specificity, and where possible, acceptable alternative systems that are less sensitive or specific are suggested for laboratories lacking facilities for C purification.

Animals↗
PubMed1984

Purification and characterization of human, guinea pig and mouse C1q by fast protein liquid chromatography (FPLC).

A simple and rapid procedure for the purification of C1q from human, guinea pig and mouse serum is described. This procedure allows the purification of C1q within one and a half days using euglobulin precipitation, chromatography on Superose 6B, followed by chromatography on Mono S by Fast Protein Liquid Chromatography (FPLC). The highly purified, hemolytically active C1q is free of any immunoglobulins. Since the purification of C1q of three different species was performed by the same purification procedure, a comparison of the subunit compositions was made under reducing and non-reducing conditions on SDS-PAGE. The yield was found to be more than 50%.

Animals↗
PubMed1986

New methods for the preparation of the cellular intermediate EAC14.

The cellular intermediate EAC14 was successfully prepared by incubating optimally sensitized sheep erythrocytes (EA) with normal serum diluted in complement diluent buffer containing suitable amounts of inhibitors of EAC142 formation from EAC14 and C2, namely polymyxin E and polymyxin B. EAC14 cells could also be prepared by incubating EA with normal serum diluted in Mg2+ free complement diluent buffer in the presence or absence of sucrose. The cellular intermediates prepared by these methods exhibited characteristic EAC142 formation and decay profiles and were found to be suitable for C2 estimations.

Animals↗