Search PubMed⌕ Search

Biomedical subjects

M R Daha

Publications and source records attributed to M R Daha.

At least 469 records · Page 26Linked to original sources
PubMed1980

Experimental Streptococcus sanguis endocarditis: immune complexes and renal involvement.

An increase of agglutinins and circulating immune complexes (CIC) was observed in the sera of rabbits after the induction of bacterial endocarditis (BE) by intravenous injection of live streptococci into animals with a non-bacterial thrombotic endocarditis. Rabbits immunized for 12 days with heat-killed streptococci developed higher levels of agglutinins and CIC than did those unimmunized during BE. The levels remained elevated in the immunized rabbits after the induction of streptococcal endocarditis. In rabbits with very high levels of CIC complement activation occurred in vivo, possibly via the classical pathway. Kidneys from both unimmunized and immunized rabbits with streptococcal endocarditis contained bacteria and also showed inflammatory reactions but only the renal tissue of immunized rabbits with endocarditis showed a little mesangial deposition of immunoglobulin. The findings in this study indicate that in rabbits, renal inflammation due to BE is initiated more often by septic emboli than by immune complex deposition, at least during the first 12 days after infection.

Agglutinins↗
PubMed1980

The effect of lidocaine on the processing of soluble immune aggregates and immune complexes by peritoneal macrophages.

In a search for new techniques which would specifically identify the various steps of the handling of immune complexes by macrophages the local anaesthetic, lidocaine, was investigated. Lidocaine was shown to inhibit selectively the digestion of immune complexes and immunoglobulin aggregates by macrophages whereas it had little effect on the binding or ingestion steps. Due to the reversible inhibitory effect of lidocaine, this drug may be used in future studies to assess the role of extracellular stimuli on the fate of intracellular immune complexes.

Animals↗
PubMed1980

Circulating and tissue-bound immune complexes in allergic vasculitis: relationship between immunoglobulin class and clinical features.

Sixty-two patients with allergic vasculitis and histological evidence of leukocytoclastic vasculitis were examined to determine whether clinical features, such as course and degree of systemic involvement, could be related to the class of the immunoglobulins in immune complexes (IC) in both the circulation and the vessel wall. Circulating IC were detected with the 125I-C1q-binding assay (C1q-BA), an anti-IgA inhibition binding assay (a-IgA-Inh BA) and the conglutinin-binding assay (Con-BA). Stabilized heat-aggregated IgG, IgA and IgM were used to determine the immunoglobulin class specificity of these assays. With the C1q-BA only aggregated IgG were detected, with the a-IgA-Inh Ba only aggregates containing IgA. With the Con-BA IgG, IgA or IgM in reactive aggregates were identified with class-specific antibodies. For patients with acute cutaneous vasculitis all assays were negative. The a-IgA-Inh BA was frequently positive in sera of patients with chronic cutaneous and acute systemic vasculitis; in the latter group conglutinin-binding IC of the IgG, IgA and IgM class were also detected. Levels in the C1q-BA were high for patients with chronic systemic vasculitis. Comparison of the results of the IC assays with the immunofluorescence studies of the cutaneous vessel walls of the same patients showed agreement between the results of the C1q-BA and deposition of IgG and the results of the a-IgA-Inh BA and IgA deposition. The class of immunoglobulin in conglutinin-binding IC did not correspond as well with the immunoglobulins in vessel walls. This study shows that certain clinical features of allergic vasculitis are related to the composition of the IC in the circulation and in the vessel wall.

Adolescent↗
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↗
PubMed1979

Clearance and glomerular localization of preformed DNP anti-DNP immune complexes.

The in vivo behaviour of well-defined immune complexes in rats was studied using complexes derived from DNP-conjugated bovine thyroglobulin (DNP-BTG) and purified specific goat anti-DNP IgG. Both clearance and glomerular localization were mainly dependent on the nature of the antigen. Soluble immune complexes formed with DNP17-BTG were cleared faster and showed a more marked localization in the glomerular mesangium than complexes formed with DNP3.4-BTG. A slight increase in the antibody to antigen ratio seemed to facilitate mesangial localization of soluble immune complexes. Insoluble immune complexes showed temporary localization as microemboli in the lumina of glomerular and peritubular capillaries. This study thus shows that not only the size and composition of the complexes but also the nature of the antigen within the complex can influence the clearance and organ localization of circulating immune complexes.

Animals↗
PubMed1979

Requirement of extracellular complement and immunoglobulin for intracellular killing of micro-organisms by human monocytes.

The role of serum factors in the intracellular killing of bacteria by monocytes was studied on the basis of an assay independent of phagocytosis. After 3 min of phagocytosis of preopsonized bacteria and removal of noningested bacteria, the monocytes containing bacteria are reincubated for various periods and the number of unkilled bacteria is determined by a microbiological method after lysis of the cells. Evidence that this assay measures the killing of ingested bacteria was provided by scanning electron microscopy, lysostaphin treatment, and the effect on the rate of intracellular killing of inactivated serum lacking specific opsonic activity. Intracellular killing of Staphylococcus aureaus, S. epidermidis, and Escherichia coli by human monocytes does not occur or is low in the absence of serum, and maximal killing is only reached when fresh serum is present; intermediate values are obtained in the presence of heat-inactivated serum. These findings indicate that complement stimulates intracellular killing. Isolated heterogeneous immunoglobulin (Ig)G, pFc fragments of heterogeneous IgG, and both IgG1 and IgG3 stimulate intracellular killing of S. aureaus by monocytes to the same degree as heat-inactivated serum. Sphingomyelinase, which decreases the number of Fc receptors, and neuraminidase, which increases these receptors, respectively, decreased and increased the intracellular killing, whereas anti-monocyte serum completely abolished the stimulation of intracellular killing by inactivated serum. These results prove that interaction of the Fc receptor with the Fc part of IgG is required for the intracellular killing. Inhibition of the activation of complement components via the alternative pathway gave a considerable reduction in the intracellular killing of S. aureaus; impairment of the activation via the classical pathway had no effect. The addition of complement components to heat-inactivated serum showed that intracellular killing is maximal only when C3b is generated. Reduction of the number of C3b receptors in the membrane by trypsin or pronase decreased intracellular killing in the presence of fresh serum; anti-monocyte serum completely abolished the stimulation of intracellular killing by fresh serum. These results lead to the conclusion that intracellular killing is also dependent on the interaction between C3b and its receptor in the membrane.

Blood Bactericidal Activity↗
PubMed1979

Further evidence for the antibody nature of C3 nephritic factor (C3NeF).

C3 nephritic factor (C3NeF), found in the sera of some patients with membranoproliferative glomerulonephritis, has been shown to be composed of two heavy and two light chains, like IgG; in addition it shares antigenic determinants with IgG. Purified C3NeF binds to the amplification convertase of complement, C3b,Bb, and thereby prevents decay of its C3-cleaving potential. The capability of C3NeF to bind to C3b,Bb was used as a means for purifying C3NeF to homogeneity. The investigation described in this report suggests that binding of C3NeF to C3b,Bb occurs via the Fab portion of the molecule. Pepsin treatment of eight C3NeF preparations resulted in an average loss of 76% of C3NeF functional activity. Papain treatment induced a loss of approximately 90%. The decrease in functional activity could be attributed to the accelerated rate of dissociation of 125I-F(ab')2 and 125I-Fab fragments from stabilized cell-bound C3b,Bb. The dissociation rate of 125I-F(ab')2 from C3b,Bb was comparable with the decay of the functional activity of C3b,Bb stabilized by F(ab')2 or Fab fragments of C3NeF. Although these results suggest that the stabilizing activity of C3NeF is mediated by the Fab portion of the molecule, it was found that the Fc portion also contributes to its functional activity.

Antibodies↗
PubMed1979

Isolation and characterization of the third component of rat complement.

The third component of complement from rat plasma was isolated by precipitation with polyethyleneglycol in the presence of benzamidine, followed by chromatography of the precipitate on CM-cellulose, hydroxyapatite, and QAE A50-Sephadex, and gel-filtration on Sephadex G-200 superfine. C3 was isolated in its native form, as assessed by its specific functional activity and its immunoelectrophoretic mobility. The recovery of C3 was between 18 and 26%, and the final material was homogenous on SDS-PAGE analysis. Rat C3 has an apparent molecular weight of 187,000 and it is composed of two non-identical disulphide linked polypeptide chains of 123,000 and 76,000. A monospecific antiserum against rat C3 was produced by immunization of rabbits with purified C3. Zymosan treatment of rat serum resulted in cleavage of C3 and in the appearance of component with a greater mobility during immunoelectrophoresis. The plasma concentration of rat C3 in Wistar rats was 581 +/- 49 microgram/ml (mean +/- 1 S.D.). Interaction of highly purified rat C3 with purified human components B, D, and P resulted in the formation of a C3 convertase suggesting compatibility between human and rat C3.

Animals↗
PubMed1979

Activation of the classical pathway of complement by the C3NeF-stabilized cell-bound amplification convertase.

C3 nephritic factor (C3NeF) has been shown to be composed of two heavy and two light chains, like IgG; in addition it shares antigenic determinants with IgG. C3NeF, purified from the sera of eight patients by incorporation of C3NeF into the stabilized fluid phase amplification C3 convertase, C3bBb(C3NeF), followed by its release after decay of convertase function, was investigated for its ability to bind 125I-C1q and to activate 125I-C1. It was found that although fluid phase C3b,Bb(C3NeF) is fully capable of binding 125I-C1q, it is not able to activate 125I-C1 even at concentrations of 1.3 x 10(12) C3bBb(C3NeF) complexs/ml. On the other hand, cell-bound C3bBb(C3NeF) is capable of both binding 125I-C1q and activating 125I-C1. This discrepancy between fluid phase and cell-bound, C3bBb(C3NeF) was found for C3NeF preparations from eight different patients and therefore seems to apply to all C3NeF preparations.

Binding Sites↗
PubMed1979

Isolation of the fourth component (C4) of rat complement.

The fourth component of rat complement was purified to homogeneity by sequential chromatography of rat plasma in benzamidine on QAE-A50, SP-C50, hydroxyapatite, and gel filtration on Bio-Gel A 1.5. The final material was homogeneous on SDS-PAGE analysis and had a calculated m.w. of 198,000. A monospecific antibody against rat C4 was obtained from immunized rabbits. The concentration of rat C4 in the plasma of normal 4-month-old Wistar rats was 190 +/- 34 microgram/ml (mean +/- 1 S.D.).

Animals↗
PubMed1978

Synthesis and degradation of glomerular basement membrane in rats with nephrotoxic nephritis.

Degradation and synthesis of the collagen portion (CLP) of the glomerular basement membrane (GBM) in glomeruli of rats with nephrotoxic nephritis (NTN) were determined in vivo and in vitro. Degradation of CLP in rats with NTN was only increased during the first 24 h after induction of NTN. After 24 h, the half-life of CLP in NTN rats (16.9 days) was not significantly different from that in the controls 15.6 days). The loss of CLP during the first 24 h is accompanied by an increased synthesis, measured in vivo and in vitro. The increased synthesis, however, does not seem to be sufficiently high to result in accumulation of CLP-like material in NTN. Since degradation and synthesis of CLP was not altered during the later phase of NTN, it is unlikely that chronic proteinuria is the result of an ongoing abnormal turnover of CLP.

Animals↗
PubMed1977

Effect of indomethacin on the synthesis of glomerular basement membrane and on proteinuria in rats with nephrotoxic nephritis.

The effect of indomethacin on protein excretion and on the synthesis of glomerular basement membrane (GBM) was studied during various stages of nephrotoxic nephritis (NTN) in the rat. Daily administration of indomethacin (4 mg/kg) was instituted 1, 6, or 21 days after the induction of NTN with 210, 240, or 268 microgram kidney-fixing antibodies (KFAb). Proteinuria in rats with nephritis induced by 210 microgram KFAb decreased under treatment with indomethacin regardless of the day on which treatment was started but was not affected by indomethacin in rats with clinically more severe nephritis induced with higher doses of KFAb. GBM synthesis was measured in vivo and in vitro by determination of the incorporation of 3H-proline into the GBM. NTN rats treated with indomethacin showed increased GBM synthesis early in the course of NTN, over and above an already increased synthesis. In the later phase of NTN indomethacin treatment did not affect GBM synthesis. The absence of a relationship between the effect of indomethacin on proteinuria and its effect on GBM synthesis clearly shows that the reduction of protein excretion occurring under indomethacin treatment is not mediated by alterations in the rate of GBM synthesis.

Animals↗
PubMed1977

Pathways of complement activation in membranoproliferative glomerulonephritis and allograft rejection.

The complement system is comprised of at least 18 plasma proteins and consists of four functional divisions: two pathways for activation (classical and alternative), a common amplification mechanism for the activating pathways, and a final common effector pathway to which the activating and amplifying sequences are directed. The classical pathway is activated by certain antigen-antibody complexes, while the alternative pathway may be initiated non-immunologically by various microbial polysaccharides. Indeed, mixtures of purified C3, B, D, and P regulated to low-grade interaction by the presence of C3bINA and beta1 H respond to zymosan with amplified C3 and B inactivation. Both pathways form enzymes termed C3 convertases that cleave C3 to generate its major fragment, C3b. C3b interacts with each C3 convertase to permit C5 cleavage in activation of the effector complement sequence, and it interacts with alternative-pathway factors B and D to generate additional C3 convertase, C3bBb, in the amplification pathway. As C3 cleavage represents the most critical step in the elaboration of the biologic effects of the complement system, modulation of this reaction by generation, stabilization, and inactivation of the amplification convertase C3bBb may well determine whether initial activation of the complement sequence eventuates in beneficial or detrimental effects for the host. Initial generation of C3bBb is dependent on prior cleavage of C3, which may occur by the classical pathway or the alternative pathway. Stabilization of C3bBb is achieved with either P or C3NeF after their binding to C3b and C3bBb, respectively. Control of this amplifying step occurs at three levels: intrinsic decay of the inherently labile C3bBb complex, extrinsic decay-dissociation of Bb from the complex by beta1H, and inactivation of C3b by C3bINA. In the presence of stabilizing factors the control proteins must function in sequence, since C3bINA cannot act on C3bBb; beta1H-mediated decay of protective Bb must precede C3b inactivation by C3bINA. C3NeF, which is found in the sera of some patients with MPGN and persistent depressions of serum C3, circumvents all three controls because of its capacity to create a stabilized convertase that is relatively resistant to decay-dissociation by beta1H. The effector complement sequence is activated by cleavage of C3 and C5, which releases vasoactive and chemotactic peptides, C3a and C5a, and generates the major fragments C3b and C5b. C3b, in addition to its function in the amplifying reaction and the C5 convertases, mediates immune adherence to cells possessing membrane-associated receptors for C3b; this in turn promotes the phagocytic and secretory functions unique to each cell type. Cell-bound C5b serves to assemble the cytolytic complex C5b6789, while fluid-phase C5d generates the hemolytically inactive chemotactic complex C567d...

Complement C3↗