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Biomedical subjects

M R Daha

Publications and source records attributed to M R Daha.

At least 451 records · Page 25Linked to original sources
PubMed1981

The specific detection of IgA in immune complexes.

An assay to detect IgA in circulating immune complexes (IC) using low avidity goat IgM antibody against human polyclonal IgA is described. The binding of this antibody to IgA coupled to Sepharose 6B is inhibited by IgA-containing IC. The specificity and sensitivity of this anti-IgA inhibition assay (a-IgA-InhA), was evaluated with aggregated purified immunoglobulins, sera of patients with Henoch-Schönlein purpura and normal human sera. Aggregated immunoglobulins of the IgA class, but not monomeric IgA, were reactive. Sucrose density ultracentrifugation showed that large IgA constituents (greater than 19S) were found only in the sera of patients with Henoch-Schönlein purpura. Both these sera and normal human serum contained smaller IgA components (between 7S and 19S), probably small polymers of IgA, which were reactive in this assay and interfered with detection of IgA-containing IC. Redissolved precipitates obtained from normal serum with polyethylene glycol showed reduced reactivity in the test, whereas the inhibitory activity of IgA-containing IC in sera of patients with Henoch-Schönlein purpura was retained in the precipitates. Precipitation of sera with polyethylene glycol allowed detection of smaller quantities of IgA-containing IC in patients with Henoch-Schönlein purpura.

Antigen-Antibody Complex↗
PubMed1981

Participation of immunoglobulins and complement components in the intracellular killing of Staphylococcus aureus and Escherichia coli by human granulocytes.

Immunoglobulins and complement components are required for optimal ingestion and optimal killing of microorganisms by granulocytes. The degree of opsonization of microorganisms necessary for their ingestion was lower than that required for the killing of these bacteria during the ingestion phase. Killing during this phase was found to depend mainly on the presence of heat-labile opsonins, probably C3b, present on the microorganisms. Extracellular immunoglobulin G (IgG) and C3b were indispensable for optimal intracellular killing after ingestion was complete. This was established with an assay permitting assessment of the course of the number of viable intracellular bacteria independent of the ingestion of new live bacteria. Maximal intracellular killing by human granulocytes of ingested catalase-positive (Staphylococcus aureus and Escherichia coli) or catalase-negative (Streptococcus pyogenes and S. pneumoniae) microorganisms was found only when fresh serum was present extracellularly. Killing was suboptimal in the absence of serum. With heat-inactivated serum, the killing index lay between the indices obtained in the presence and absence of fresh serum. The stimulatory activity of heat-inactivated serum was most probably due to the interaction of IgG with the Fc receptor on the granulocyte membrane, since IgG subclasses IgG1 and IgG3 as well as pFc fragments of IgG stimulated the intracellular killing to the same degree as heat-inactivated serum did. In addition, (Fab1)2 fragments of IgG did not stimulate killing, and reduced killing was observed in the presence of heat-inactivated serum after reduction of the number of Fc receptors. The extra stimulation of the killing process in the presence of fresh serum compared with heat-inactivated serum was due to the interaction between membrane receptors and complement--most probably C3b generated by both the classical and the alternative pathways of complement activation. This conclusion is based on results obtained with sera in which one or both complement pathways were blocked, on the restoration of the killing-stimulatory activity of C3-deficient serum after addition of fresh C3, and on the reduced killing observed in the presence of fresh serum after reduction of the number of C3 receptors by the use of pronase or antigranulocyte serum.

Blood Bactericidal Activity↗
PubMed1981

Enhanced degradation of soluble immune complexes by guinea-pig peritoneal macrophages in the presence of complement.

The role of complement in the processing of soluble immune complexes by guinea-pig peritoneal macrophages was studied in an homologous system in vitro by using immune complexes prepared with bovine thyroglobulin as the antigen and guinea-pig IgG2 antibodies. The simplest complexes showing complement activation and which were degradable by macrophages had a composition of Ag1 Ab2-3. Complement was shown to have an enhancing effect on the degradation of complexes which had an antibody: antigen ratio in the complexes which was at least 4 (Ag1 Ab4). The effect of size on complement activation and degradation of the complexes by macrophages was studied by employing the observation that immune complexes increase in size during their preparation. In the presence of serum as a complement source it was shown that degradation of small complexes by macrophages was inhibited whereas the degradation of large complexes was enhanced. The enhanced degradation of complexes in the presence of fresh serum did not occur in C4-deficient serum nor in EDTA-serum, which indicates that the observed effect is complement mediated. The experiments described here thus extend and confirm earlier studies using heat aggregated immunoglobulins and show that complement may play an important role in the elimination of immune complexes in vivo.

Animals↗
PubMed1981

Enhanced alternative complement pathway-dependent degradation of soluble immunoglobulin aggregates by macrophages.

The role of complement in the processing of soluble immune aggregates by guinea-pig peritoneal macrophages was studied in a homologous system in vitro. Stable soluble aggregates of guinea-pig IgG1 are shown to activate the alternative pathway in C4-deficient guinea-pig serum. At 37 degrees and under serum-free conditions, adherent peritoneal macrophages degraded in 2 hr at least 50% of the available immunoglobulin aggregates. Addition of fresh C4D serum to the incubation mixtures caused a two-fold increase in the rate of degradation. The stimulating effect of C4D serum was complement-mediated, because it was abolished by heat treatment, CoVF treatment and specific C3 depletion of the C4D serum. Functional inactivation of C3 receptors on the macrophages by trypsin also impeded the stimulating effect of fresh C4D serum. The results indicate that the alternative pathway of complement contributes significantly to the elimination of soluble immune complexes by mononuclear phagocytes.

Animals↗
PubMed1980

Circulating immune complexes and thyroid-stimulating immunoglobulins before, during, and after antithyroid drug therapy in patients with Graves' disease.

Sera from patients with Graves' disease were assayed for thyroid-stimulating immunoglobulins (TSI) and circulating immune complexes (CIC) before, during, and after antithyroid drug treatment. 41 (72%) of 57 untreated patients had a positive TSI index and 17 (30%) had CIC. In untreated patients CIC were significantly more common in patients with a negative TSI index than in those with a positive one. It is suggested that because CIC prevent TSI from being detected the TSI index may be negative in Graves' disease. Early in the course of the treatment CIC developed in 85% of the patients; in all of these patients TSI disappeared. Later in the course of treatment when CIC could no longer be detected TSI did not reappear. These findings indicate that the development CIC could be the manifestation of the re-establishment of a natural tolerance to thyroid-stimulating hormone receptors in patients with Graves' disease.

Antibodies, Anti-Idiotypic↗
PubMed1980

Allergic vasculitis. A histological and immunofluorescent study of lesional and non-lesional skin in relation to circulating immune complexes.

This study concerns 57 patients who fulfilled histological criteria for the diagnosis allergic vasculitis. For 37 of these patients, biopsy specimen were available from lesional and adjacent non-lesional skin. Histological signs of vasculitis were found at both sites, but in clinically normal skin the perivascular infiltrate was less dense and neutrophils and eosinophils were sparse or absent. Fibrin was found in only ten patients and occurred less frequently in non-lesional skin. Deposits of immune complexes and/or complement were detected by immunofluorescence in 49 of the 57 patients. Hardly any differences between lesional and non-lesional skin were found with immunofluorescent microscopy. Circulating immune complexes were detected in 45 of the 56 available sera. A relationship was found between the class of immunoglobulin in immune complexes in the vessel wall and in the circulation. Moreover, the class of immunoglobulin seemed to be related to the course, the extracutaneous involvement, and the presence of associated diseases. No explanation was found for the histological differences observed between lesional and non-lesional skin.

Antigen-Antibody Complex↗
PubMed1980

Circulating IgA-immune complexes in Henoch-Schönlein purpura. A longitudinal study of their relationship to disease activity and vascular deposition of IgA.

In Henoch-Schönlein purpura immune complexes in inflamed vessel walls characteristically contain immunoglobulin A(IgA). To determine whether IgA is also the predominant immunoglobulin in circulating immune complexes, we compared the results of three immune complex assays with specificities for different classes of immunoglobulins in a longitudinal study of 37 patients (30 children and seven adults) with Henoch-Schönlein purpura. Circulating IgA-containing immune complexes were detected by their reactivity with a low avidity anti-IgA antibody in 27 of the 37 patients. IgA was simultaneously present in cutaneous vessel walls in 95 percent of the patients with circulating IgA-containing immune complexes. High levels of IgA-containing immune complexes were found only during the initial phase of the disease. Immune complexes containing bound complement breakdown products were demonstrated by binding to conglutinin. IgA was found in these immune complexes in 17 patients, IgG in 17 and IgM in nine patients. There was no apparent relation with the class of immunoglobulin in the deposits. Conglutinin-binding immune complexes were present later in the course of the disease and after remission. C1q-binding immune complexes were only found in two patients. These findings suggest that immune complexes-containing IgA may initiate the vasculitis of Henoch-Schönlein purpura, whereas complement-reacted immune complexes containing immunoglobulins of the other classes appear in the circulation in a later phase.

Adolescent↗
PubMed1980

Stabilization of the classical pathway C3 convertase C42, by a factor F-42, isolated from serum of patients with systemic lupus erythematosus.

Sera from sixteen patients with SLE were investigated for the presence of a factor which would conserve convertase activity on preformed EAClgp 4hu2hu for 30 min at 30 degrees in EDTA. Although such a factor could not be detected readily in the sera, chromatography on DE-52 cellulose yielded fractions appearing as three peaks in one patient and as two peaks in a second patient. These peaks were capable of conserving C42 activity and were designated as F-42. Purification of F-42 from the second peak eluting between 4 and 7 mS on DE-52 was obtained by SP-C50, S-300 and QAE-A50 chromatography. F-42 exhibited charge heterogeneity upon SP-C50 chromatography. On polyacrylamide gel electrophoresis the final material migrated as one band, which coincided with the position of F-42 activity upon eluation from a parallel gel. F-42 had an apparent molecular weight of 150,000 and reacted with anti-IgG in Ouchterlony analysis. Sepharose-bound anti-IgG was capable of neutralizing F-42 activity. The purified material was shown to prolong the half-life (T 1/2) of performed cell-bound C42 in GVB-EDTA at 30 degrees from 5 to 80 min.

Antibodies↗
PubMed1980

Relative resistance of the F-42-stabilized classical pathway C3 convertase to inactivation by C4-binding protein.

The sera of some patients with SLE contain an IgG antibody (F-42) directed against the classical pathway C3 convertase (C-42), which is capable of stabilizing C42 in a dose-dependent manner. The half-life (T 1/2) of C42 is prolonged by F-42. In order to determine whether C4-binding protein was capable of reversing stabilization of C42, stabilized and unstabilized cell-bound C42 were exposed to purified C4-bp and the convertase activity was assessed. C4-bp was capable of accelerating the decay of C42 in a dose-dependent manner; 2 microgram/ml C4-bp reduced the T 1/2 of C42 from 5 to 2.5 min at 30 degrees C. On the other hand, 16 microgram C4-bp could reverse stabilization of C42 by F-42 from T 1/2 = 78 min to a T 1/2 - 40 min; 128 microgram C4-bp reduced the T 1/2 of stabilized C42 to 4 min. Functional inactivation of C42 occurs via enhanced decay-dissociation of C2 from the convertase by C4-bp, as shown by the release of 125I-C2i from the cell-bound convertase. Stabilization of C42 by F-42 is caused by prevention of decay-dissociation of 125I-C2. F-42 was also capable of stabilizing C4oxy2 even further, as shown by prolongation of the T 1/2 of cell-bound C4 oxy2 to a T 1/2 of at least 300 min at 30 degrees C.

Antibodies↗
PubMed1980

Isolation and characterization of rat complement factor B and its interaction with cell-bound human C3.

Factor B was isolated from fresh rat plasma by sequential chromatography on QAE-A50, Biorex-70, gel filtration on Sephadex G-200 superfine and rechromatography on QAE-A50. That Brat was isolated in its native form was indicated by its migration during immunoelectrophoresis and by its capacity to react with cobra venom factor (CoVF) in the presence of human D to form a C3 convertase capable of cleaving purified rat C3 and human C3. The recovery of Brat was between 8 and 15%; the final material was homogeneous according to SDS-PAGE analysis. Reduction of Brat with DTT in the presence of urea and SDS did not produce detectable peptides of lower molecular weight. Both reduced and unreduced Brat had an apparent molecular weight of 100,000. An antiserum against Brat induced in rabbits recognized only one protein in fresh rat plasma as indicated by immunodiffusion and immunoelectrophoretic analysis. Zymosan treatment of rat serum resulted in the cleavage of Brat into two fragments with alpha and gamma mobility. Native Brat has a beta electrophoretic mobility. The plasma concentration of Brat in Wistar rats was 215 +/- 38 microgram/ml (mean +/- SD).

Animals↗
PubMed1980

Isolation and characterization of feline C3 and evidence for the immune complex pathogenesis of feline infectious peritonitis.

Infections of cats with feline peritonitis (FIP) virus are usually inapparent but may lead to fatal polyserositis. We have recently advanced the hypothesis that immune complexes play an essential role in the pathogenesis of the condition. To support this hypothesis, the role of the third component of complement in FIP was investigated. In the present paper, the isolation of C3 from normal cat serum and some of its physical and immunologic properties are described. The final protein had an apparent m.w. of 185,000 and was composed of 2 polypeptide chains with m.w. of 128,000 and 71,000, respectively. When tested against whole cat serum, an antiserum raised in rabbits against purified C3 recognized only 1 protein whose identity with C3 was established. With the aid of this antiserum, depositions of C3 in renal glomeruli of FIP-affected cats were demonstrated by immunofluorescence. Their localizaton coincided with that of deposited IgG, thereby supporting the concept of an immune complex pathogenesis of FIP.

Animals↗