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M C Carroll

Publications and source records attributed to M C Carroll.

At least 55 records · Page 3Linked to original sources
PubMed1998

Acute nephrotoxic serum nephritis in complement knockout mice: relative roles of the classical and alternate pathways in neutrophil recruitment and proteinuria.

BACKGROUND: The importance of complement in the pathophysiology of renal disease is still being appreciated. To further address the role of this mediator system, we evaluated the influence of absolute deficiency of C3 and C4 on acute nephrotoxic serum nephritis (NSN). METHODS: Selective 'knockout' of C3 and C4 was routinely confirmed in null mice by ELISA. NSN was induced by intravenous injection of a sheep anti-rat nephrotoxic serum that cross-reacts with murine glomerular antigens. Deposition of heterologous immunoglobulin in wild-type glomeruli was associated with rapid complement deposition and neutrophil infiltration, and followed by the development of proteinuria. RESULTS: Neutrophil infiltration was markedly inhibited in C3-deficient mice indicating a role for complement in PMN recruitment. In contrast, C3 deficiency afforded only partial protection against proteinuria. NSN was studied further in C4 null mice to probe the relative roles of the classical and alternate pathway in disease pathophysiology. C3 and C4 deficiency were associated with equivalent inhibition of PMN recruitment and proteinuria. CONCLUSIONS: In aggregate, the data support a major role for complement in PMN recruitment in this model and point to complement-independent mechanisms of proteinuria in antibody-mediated glomerulonephritis. These 'knockout' mice should prove valuable for defining the complement-activated mediator systems that regulate leukocyte recruitment and tissue injury in renal diseases.

Acute Disease↗
PubMed1998

The role of complement and complement receptors in induction and regulation of immunity.

Covalent attachment of activated complement C3 (C3d) to antigen links innate and adaptive immunity by targeting antigen to follicular dendritic cells (FDC) and B cells via specific receptors CD21 and CD35. Recent characterization of knockout mice deficient in complement components C3, C4, or the receptors CD21 and CD35 as well as biochemical studies of the CD21/CD19/Tapa-1 coreceptor on B cells have helped to elucidate the mechanism of complement regulation of both B-1 and B-2 lymphocytes. Interestingly, natural antibody of the adaptive immune system provides a major recognition role in activation of the complement system, which in turn enhances activation of antigen-specific B cells. Enhancement of the primary and secondary immune response to T-dependent antigens is mediated by coligation of the coreceptor and the B cell antigen receptor, which dramatically increases follicular retention and B cell survival within the germinal center. Most recent evidence suggests that complement also regulates elimination of self-reactive B cells, as breeding of mice that are deficient in C4 or CD21/CD35 with the lupus-prone strain of lpr mice demonstrates an exacerbation of disease due to an increase in autoantibodies.

Animals↗
PubMed1998

A small molecular weight factor in aqueous humor acts on C1q to prevent antibody-dependent complement activation.

PURPOSE: Aqueous humor inhibits activation of the classic complement pathway; however, the mechanism of this inhibition is unknown. We have examined at the molecular level potential factors responsible for the inhibition, and we have tried to determine where in the complement pathway the inhibition takes place. METHODS: Fresh rabbit aqueous humor was size fractionated by centrifuge concentrators and by size exclusion column chromatography, and each fraction was assayed for inhibition of the classic complement pathway in a standard CH50 hemolytic assay. Fractions with inhibitory activity were assayed for protein and the presence of ascorbic acid and were subjected to heat treatment. To identify where in the pathway the inhibitor(s) function, the expression of activated complement components bound to the surface of antibody-coated erythrocytes was analyzed by flow cytometry using fluorescein isothiocyanate-labeled antibodies to specific complement components. In addition, hemolytic assays were performed for the function of individual complement components. RESULTS: The most potent inhibition of the classic pathway was in a fraction of aqueous humor of less than 1.3 kDa. The inhibitory activity in the fraction was unassociated with detectable protein or ascorbic acid, and it remained present after heat treatment. The functional analysis through flow cytometry and hemolytic assays for individual complement components showed that the inhibitor in the less than 1.3-kDa fraction caused a blockade in the complement pathway at the level of C1q. CONCLUSIONS: The aqueous humor contains a unique potent anticomplementary factor that has a molecular weight less than 1.3 kDa. This heat-stable inhibitory factor inhibits the classic pathway at the level of C1q. These results imply that within the eye the complement pathway is inhibited at the earliest steps of its initiation. Such inhibition would prevent production of complement products that mediate inflammation and chemotaxis of inflammatory cells. Therefore, as part of the adaptation of immune privilege, the ocular microenvironment is protected from inflammation induced by antigen-antibody complexes.

Animals↗
PubMed1997

A role for Mac-1 (CDIIb/CD18) in immune complex-stimulated neutrophil function in vivo: Mac-1 deficiency abrogates sustained Fcgamma receptor-dependent neutrophil adhesion and complement-dependent proteinuria in acute glomerulonephritis.

Mac-1 (alphambeta2), a leukocyte adhesion receptor, has been shown in vitro to functionally interact with Fcgamma receptors to facilitate immune complex (IC)-stimulated polymorphonuclear neutrophil (PMN) functions. To investigate the relevance of Mac-1-FcgammaR interactions in IC-mediated injury in vivo, we induced a model of Fc-dependent anti-glomerular basement membrane (GBM) nephritis in wild-type and Mac-1-deficient mice by the intravenous injection of anti-GBM antibody. The initial glomerular PMN accumulation was equivalent in Mac-1 null and wild-type mice, but thereafter increased in wild-type and decreased in mutant mice. The absence of Mac-1 interactions with obvious ligands, intercellular adhesion molecule 1 (ICAM-1), and C3 complement, is not responsible for the decrease in neutrophil accumulation in Mac-1- deficient mice since glomerular PMN accumulation in mice deficient in these ligands was comparable to those in wild-type mice. In vitro studies showed that spreading of Mac-1-null PMNs to IC-coated dishes was equivalent to that of wild-type PMNs at 5-12 min but was markedly reduced thereafter, and was associated with an inability of mutant neutrophils to redistribute filamentous actin. This suggests that in vivo, Mac-1 is not required for the initiation of Fc-mediated PMN recruitment but that Mac-1-FcgammaR interactions are required for filamentous actin reorganization leading to sustained PMN adhesion, and this represents the first demonstration of the relevance of Mac-1-FcgammaR interactions in vivo. PMN-dependent proteinuria, maximal in wild-type mice at 8 h, was absent in Mac-1 mutant mice at all time points. Complement C3-deficient mice also had significantly decreased proteinuria compared to wild-type mice. Since Mac-1 on PMNs is the principal ligand for ic3b, an absence of Mac-1 interaction with C3 probably contributed to the abrogation of proteinuria in Mac-1-null mice.

Actins↗
PubMed1997

Impaired mast cell-dependent natural immunity in complement C3-deficient mice.

The complement system is widely regarded as essential for normal inflammation, not least because of its ability to activate mast cells. However, recent studies have called into question the importance of complement in several examples of mast cell-dependent inflammatory responses. To investigate the role of complement in mast cell-dependent natural immunity, we examined the responses of complement-deficient mice to caecal ligation and puncture, a model of acute septic peritonitis that is dependent on mast cells and tumour necrosis factor-alpha (TNF-alpha). We found that C4- or C3-deficient mice were much more sensitive to caecal ligation and puncture than wild-type (WT) controls (100% versus 20% in 24-h mortality, respectively). C3-deficient mice also exhibited reductions in peritoneal mast cell degranulation, production of TNF-alpha, neutrophil infiltration and clearance of bacteria. Treating the C3-deficient mice with purified C3 protein enhanced activation of peritoneal mast cells, TNF-alpha production, neutrophil recruitment, opsonophagocytosis of bacteria and resistance to caecal ligation and puncture, confirming that the defects were complement-dependent. These results provide formal evidence that complement activation is essential for the full expression of innate immunity in this mast cell-dependent model of bacterial infection.

Animals↗
PubMed1997

A macrophage invasion mechanism of pathogenic mycobacteria.

Tuberculosis is the leading cause of death due to an infectious organism, killing an estimated 3 million people annually. Mycobacterium tuberculosis, the causative agent of tuberculosis, and other pathogenic mycobacteria require entry into host macrophages to initiate infection. An invasion mechanism was defined that was shared among pathogenic mycobacteria including M. tuberculosis, M. leprae, and M. avium but not by nonpathogenic mycobacteria or nonmycobacterial intramacrophage pathogens. This pathway required the association of the complement cleavage product C2a with mycobacteria resulting in the formation of a C3 convertase. The mycobacteria-associated C2a cleaved C3, resulting in C3b opsonization of the mycobacteria and recognition by macrophages.

Amino Acid Sequence↗
PubMed1997

Endotoxin shock in antibody-deficient mice: unraveling the role of natural antibody and complement in the clearance of lipopolysaccharide.

While the significance of natural Ab is not entirely clear, one proposed role is clearance of bacterial Ags. To determine whether natural Ab was involved in clearance of endotoxin, we have examined novel strains of mice with either a total or selective deficiency in Ig. Recombinase-activating gene-2 (RAG-2(-/-))-deficient mice, which have no serum Ig due to arrested development of B cells at the pro-B stage, demonstrate increased sensitivity to endotoxin that correlates with an impaired clearance. When RAG-2(-/-) mice are reconstituted with pooled sera from normal mice, both survival and clearance of circulating endotoxin are enhanced. To further define the nature of the protective Ab, Bruton's tyrosine kinase (Btk)-deficient mice were characterized in the high dose LPS model. Like RAG-2(-/-) mice, they are highly sensitive to endotoxin and have an impaired clearance of LPS. Reconstitution of Btk(-/-) mice, which have reduced levels of IgG3 and IgM, with purified normal mouse IgM dramatically enhances their ability to clear endotoxin compared with mock (saline)-reconstituted littermates. The cellular source of natural anti-LPS IgM was identified as the peritoneal-residing B-1 cell by enzyme-linked immunospot (ELISPOT) assay. Taken together, these studies demonstrate the important role of natural Ab and complement in the clearance of pathogenic substances from the circulation.

Animals↗
PubMed1997

Increased susceptibility to endotoxin shock in complement C3- and C4-deficient mice is corrected by C1 inhibitor replacement.

Endotoxin shock is a life-threatening syndrome associated with a Gram-negative infection and mediated by a systemic inflammatory response. As a major effector of inflammation, the complement system has been implicated in both the pathogenesis and the protection from endotoxin shock. To clarify the role of complement in endotoxin shock, we have used mice totally deficient in either complement component C3 or C4. We found that both the C3- and C4-deficient mice were significantly more sensitive to endotoxin than wild-type controls. The endotoxin-challenged complement-deficient mice failed to clear endotoxin efficiently from the circulation and this led to excess consumption of C1 inhibitor protein (C1 INH), a major regulator of both complement and the contact system of blood coagulation. Replacement of C1 INH rescued the endotoxin-challenged complement-deficient mice from shock and death. These findings suggest a novel therapy for treatment of endotoxemia with C1 INH protein.

Animals↗
PubMed1997

Complement and the immune response.

This past year has seen a major advance in our understanding of how the complement system enhances the adaptive immune response. The use of in vivo models has revealed that direct coupling of C3d to antigen is sufficient to dramatically reduce the amount of antigen required for a secondary response. At least one important requirement for the enhancing effect was determined to be expression of the CD21 (C3d receptor) on B cells.

Animals↗
PubMed1997

Protection against anti-glomerular basement membrane (GBM)-mediated nephritis in C3- and C4-deficient mice.

Mice rendered completely deficient of the complement components C3 or C4 were used to determine the influence of complement activation in the heterologous phase of the anti-GBM disease model. In wild-type animals the disease is characterized by a neutrophil infiltrate, capillary thrombosis, proteinuria and C3 and C4 deposited within the glomerulus. The early infiltration of neutrophils into the glomeruli is greater in wild-type mice (2.8 +/- 0.3) compared with C3-deficient (1.4 +/- 0.2) and C4-deficient (1.2 +/- 0.003) mice. Deficiency also protects against the subsequent development of proteinuria (2.99 +/- 1.11 mg/24h, 0.059 mg/24h and 0.327 +/- 0.14 mg/24h in wild-type, C3-deficient and C4-deficient mice, respectively) and decreases glomerular capillary thrombosis in both C3- and C4-deficient mice. The degree of protection is greater in the C3-deficient than the C4-deficient animals, suggesting both classical and alternative pathway involvement. These studies support a critical role for complement in the development of anti-GBM disease. However, the protective effect of complement deficiency can be broken if the dose of nephritogenic antibody is increased.

Albuminuria↗
PubMed1997

Technetium-99m methoxy isobutyl isonitrile (MIBI) imaging of the parathyroid glands in patients with renal failure.

BACKGROUND: Technetium-99m methoxy isobutyl isonitrile (Tc-99m MIBI) scintigraphy has been reported to be at least as reliable as thallium-technetium subtraction imaging in the preoperative localization of hyperplastic parathyroid glands in patients with renal failure. Reports have suggested that 50% of glands can be identified correctly by this method. The aim of this study was to improve on previous results and demonstrate that Tc-99m MIBI imaging has an important place in the preoperative work-up of these patients. METHODS: Eighteen patients on renal replacement therapy were studied. All had tertiary hyperparathyroidism and had Tc-99m MIBI imaging prior to parathyroidectomy. A refined reporting method was employed. The imaging results were compared to the subsequent surgical and histological findings. RESULTS: In the 12 patients in whom serum parathyroid hormone levels fell postoperatively to within or below the normal range, 38 of 46 glands (82.6%) were correctly identified and located in the correct quadrant of the thyroid gland. There were two false positive results where the imaging predicted glands not subsequently found by the surgeon. In the patients who had post-operative hyperparathyroidism, repeat Tc-99m MIBI imaging was able to locate accurately the site of the residual parathyroid tissue. CONCLUSIONS: Tc-99m MIBI imaging is able to identify more than 80% of hyperplastic parathyroid glands in renal failure patients if this reporting process is used, and locate them in the correct quadrant of the thyroid gland. Tc-99m MIBI imaging is of particular value when re-exploration of the neck is required for post-parathyroidectomy hyperparathyroidism. These results represent a significant improvement on the sensitivity of this imaging technique when compared to previous published data.

Adult↗
PubMed1997

Experimental murine acid aspiration injury is mediated by neutrophils and the alternative complement pathway.

Acid aspiration may result in the development of the acute respiratory distress syndrome, an event associated with significant morbidity and mortality. Although once attributed to direct distal airway injury, the pulmonary failure after acid aspiration is more complex and involves an inflammatory injury mediated by complement (C) and polymorphonuclear leukocytes. This study examines the injurious inflammatory cascades that are activated after acid aspiration. The role of neutrophils was defined by immunodepletion before aspiration, which reduced injury by 59%. The injury was not modified in either P- or E-selectin-knockout mice, indicating that these adhesion molecules were not operative. C activation after aspiration was documented with immunochemistry by C3 deposition on injured alveolar pneumocytes. Animals in which C activation was inhibited with soluble C receptor type 1 (sCR1) had a 54% reduction in injury, similar to the level of protection seen in C3-knockout mice (58%). However C4-knockout mice were not protected from injury, indicating that C activation is mediated by the alternative pathway. Finally, an additive effect of neutrophils and C was demonstrated whereby neutropenic animals that were treated with sCR1 showed an 85% reduction in injury. Thus acid aspiration injury is mediated by neutrophils and the alternative C pathway.

Animals↗
PubMed1996

The route of antigen entry determines the requirement for L-selectin during immune responses.

L-selectin, an adhesion molecule constitutively expressed on leukocytes, is important for primary adhesion and extravasation of lymphocytes at specialized high endothelial venules within lymph nodes and other leukocytes at sites of inflammation. We have generated L-selectin-deficient mice by targeted disruption, and have confirmed a previously reported phenotype which includes strikingly impaired contact hypersensitivity (CHS) responses to reactive haptens (Tedder, T.F., D.A. Steeber, and P. Pizcueta. 1995. J. Exp. Med. 181:2259-2264; Xu, J.C., I.S. Grewal, G.P. Geba, and R.A. Flavell. 1996. 183:589-598.). Since the mechanism of this impairment has not been clarified, we sought to define the stage(s) at which the CHS response is affected in L-selectin-deficient mice. We show that epidermal Langerhans cells in L-selectin-deficient mice are normal in number, migrate to peripheral lymph nodes appropriately, and are functional in presenting allogeneic and haptenic antigens. Moreover, T cells, as well as neutrophil and monocyte effector populations, are fully capable of entry into the inflamed skin sites in the absence of L-selectin. Thus, antigen presentation and effector mechanisms are intact in L-selectin deficient mice. In contrast, virtually no antigen-specific T cells can be found within draining peripheral nodes after a contact challenge, suggesting that the defect resides primarily in the inability of antigen-specific T cells to home to and be activated in these nodes. Indeed, L-selectin-deficient mice mount completely normal CHS responses when alternate routes of immunization are used. These studies pinpoint the lesion in CHS to a discrete stage of the afferent limb of the response, clarify the role of L-selectin on effector populations, and illustrate the critical importance of the route of antigen entry to the successful execution of an immune response.

Adoptive Transfer↗
PubMed1996

Immunoglobulin G-mediated inflammatory responses develop normally in complement-deficient mice.

The role of complement in immunoglobulin G-triggered inflammation was studied in mice genetically deficient in complement components C3 and C4. Using the reverse passive Arthus reaction and experimental models of immune hemolytic anemia and immune thrombocytopenia, we show that these mice have types II and III inflammatory responses that are indistinguishable from those of wild-type animals. Complement-deficient and wild-type animals exhibit comparable levels of erythrophagocytosis and platelet clearance in response to cytotoxic anti-red blood cell and antiplatelet antibodies. Furthermore, in the reverse passive Arthus reaction, soluble immune complexes induce equivalent levels of hemmorhage, edema, and neutrophillic infiltration in complement-deficient and wild-type animals. In contrast, mice that are genetically deficient in the expression of Fc receptors exhibit grossly diminished reactions by both cytotoxic antibodies and soluble immune complexes. These studies provide strong evidence that the activation of cell-based Fc gamma R receptors, but not complement, are required for antibody-triggered murine inflammatory responses.

Anemia, Hemolytic↗
PubMed1996

Regulation of the B cell response to T-dependent antigens by classical pathway complement.

Mice deficient in complement components C3 (C3 -/-) and C4 (C4 -/-) were found to have a profound defect in their Ab response to a T-dependent Ag (bacteriophage (phi X174). Characterization of the deficient mice demonstrated a diminished level of peanut agglutinin+ germinal centers and a failure in isotype switching despite normal B cell signaling in vitro. The nature of the defect was found to lie at the B cell level, as the T cells were primed in C3- and C4-deficient mice as well as those in wild-type mice. These results, and the finding that the defect could be partly reversed by a 10-fold increase in Ag dose, support the hypothesis that covalent attachment of complement ligands, i.e., C3b and C3d to the Ag-Ab complex, increases its immunogenicity.

Animals↗
PubMed1996

Reperfusion injury of ischemic skeletal muscle is mediated by natural antibody and complement.

Reperfusion of ischemic tissue induces an acute inflammatory response that can result in necrosis and irreversible cell injury to both local vascular endothelium and parenchyma. To examine the pathogenesis of ischemia/reperfusion injury, we have used mice deficient in complement components C3, C4, or serum immunoglobulin in a hindlimb model of ischemia. We found that mice homozygous deficient in C3 or C4 were equally protected against reperfusion injury based on a significant reduction in leakage of radiolabeled albumin out of the vasculature. This demonstrates that classical pathway complement is an important factor in the initiation of inflammation following reperfusion. Furthermore, mice deficient in serum immunoglobulin were equally protected and this protection could be reversed by reconstitution with serum from normal mice. Thus, this report describes a novel mechanism for reperfusion injury that involves antibody deposition and activation of complement leading to inflammation permeability.

Animals↗
PubMed1996

Antibody response to a T-dependent antigen requires B cell expression of complement receptors.

Several lines of evidence indicate that antibody responses to T-dependent antigens require complement receptors expressed on either B lymphocytes or follicular dendritic cells. We have used RAG-2 deficient blastocyst complementation to create mice specifically lacking B cell complement receptors. Despite normal expression of complement receptor 1 (CR1[CD35]) and CR2 (CD21) on follicular dendritic cells, these mice have a profound defect in their capacity to mount a T-dependent antibody response. This is the first direct demonstration in vivo that B cell expression of complement receptors is required for a humoral immune response. This is the first direct demonstration in vivo that B cell expression of complement receptors is required for a humoral immune response. This suggests that CD21 and/or CD35 on B lymphocytes may be required for cellular activation, adsorptive endocytosis of antigen, recruitment to germinal centers, and/or protection from apoptosis during the humoral response to T-dependent antigens.

Animals↗