A reexamination of the role of magnesium in the human alternative pathway of complement

In this study the physiological role of properdin and the differential subunit composition of the solid phase enzymes of the pathway have been explored. Cell-bound C3 and C5 convertase differ in their C3b requirement. Apparently one molecule of C3b is sufficient to allow formation of C3 convertase (C3b,B), whereas two or more are required for generation of C5 convertase (C3bn,B). This conclusion was drawn from results indicating the critical role of the spacial distribution of C3b molecules on the cell surface in enzyme formation. While the C3/C5 convertase is fully capable of acting on C5 and thereby initiating the assembly of the cytolytic membrane attack complex, it is exceedingly labile and vulnerable to destruction by the C3b inactivator. It is the apparent role of properdin to confer a degree of stability upon the labile enzyme and to protect its C3 convertase function against enzymatic destruction. To achieve these effects, precursor properdin (pre-P) is recruited in a binding-activation reaction by the labile C3/C5 convertase. Multiple C3b molecules appear to be needed for the formation of properdin-activating principle. Three modes of regulation have been described, which involve spontaneous dissociation enzymatic degradation by C3b inactivator and disassembly by beta1H. The functional differences of pre-P and activated properdin (P) were delineated, pre-P displaying a weak affinity for C3b and P the capacity of strong interaction, P generating a soluble C3 convertase in serum and pre-P being unable to do so. Because of the profound differences between native pre-P and the laboratory product P, the question was raised as to whether soluble P represents an unphysiological form of the protein. On the basis of this and other studies, the conclusion was reached that in vitro properdin recruitment constitutes the terminal event of the properdin pathway, and that properdin augments the function of C3/C5 convertase without changing its substrate specificity.

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Impaired opsonophagocytosis of serotypes Ib and II of group B streptococci as compared with serotypes Ia and III: role of the alternative pathway of complement in opsonisation of serotype III of group B streptococci.

Journal of Clinical Pathology ◽

10.1136/jcp.37.7.790 ◽

1984 ◽

Vol 37 (7) ◽

pp. 790-795 ◽

Cited By ~ 1

Author(s):

P Hindocha ◽

R Hill ◽

C B Wood ◽

U Patel ◽

G Hunt

Keyword(s):

Alternative Pathway ◽

Group B Streptococci ◽

Alternative Pathway Of Complement ◽

Group B

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Analysis of Factor D Isoforms in Malpuech–Michels–Mingarelli–Carnevale Patients Highlights the Role of MASP-3 as a Maturase in the Alternative Pathway of Complement

The Journal of Immunology ◽

10.4049/jimmunol.1700518 ◽

2017 ◽

Vol 199 (6) ◽

pp. 2158-2170 ◽

Cited By ~ 20

Author(s):

Rasmus Pihl ◽

Lisbeth Jensen ◽

Annette G. Hansen ◽

Ida B. Thøgersen ◽

Stephanie Andres ◽

...

Keyword(s):

Alternative Pathway ◽

Alternative Pathway Of Complement

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Role of the alternative pathway of complement in ischemia/reperfusion and chronic graft injury in a mouse model of kidney allograft

Immunobiology ◽

10.1016/j.imbio.2012.08.207 ◽

2012 ◽

Vol 217 (11) ◽

pp. 1201

Author(s):

Regiane Aparecida Cavinato ◽

Nadia Azzollini ◽

Federica Casiraghi ◽

Marta Todeschini ◽

Giuseppe Remuzzi ◽

...

Keyword(s):

Mouse Model ◽

Alternative Pathway ◽

Ischemia Reperfusion ◽

Kidney Allograft ◽

Alternative Pathway Of Complement

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Human monocyte spreading induced by factor Bb of the alternative pathway of complement activation. A possible role for C5 in monocyte spreading.

Journal of Experimental Medicine ◽

10.1084/jem.154.3.763 ◽

1981 ◽

Vol 154 (3) ◽

pp. 763-777 ◽

Cited By ~ 33

Author(s):

J S Sundsmo ◽

O Götze

Keyword(s):

Alternative Pathway ◽

Human Monocyte ◽

Inhibitory Effect ◽

Antibody Fragments ◽

Polyacrylamide Gel ◽

Fluorescent Antibody Technique ◽

Antibody Technique ◽

Serum Free ◽

Alternative Pathway Of Complement

The central serine esterase of the alternative pathway of complement (APC) activation, activated factor B (Bb), has been shown recently to induce murine macrophages and human monocytes to become spread on a glass substrata. It has also been established that to induce the spreading reaction, the catalytic site of the Bb enzyme must be structurally intact since treatment of Bb with heat (56 degrees C for 30 min) or diisopropylfluorophosphate (10(-3) M) destroyed both enzymatic and spreading activities. In the C3b,Bb complex, Bb exhibits restricted substrate specificity for C3 and C5. With this in mind, the role of C3 and C5 in the monocyte spreading reaction was explored in the present study. Expression of C3 and C5 on the surface of human peripheral blood monocytes was investigated by the direct fluorescent antibody technique employing fluorescein isothiocyanate-conjugated anti-C3 or C5 F(ab')2 antibody fragments. It was found that C3 and C5 were present on 6 +/- 7% of freshly prepared monocytes and that expression of C5, but not C3, increased to 70 +/- 6% when monocytes were incubated for 3 d in serum-free medium. Biosynthesis of C5 was indicated when it was found that under serum-free conditions, monocytes incorporated [3H]leucine into immunoprecipitable C5 with an apparent mol wt of 180,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The role of C3 and C5 in the monocyte spreading reaction induced by factor Bb was explored by testing for the ability of anti-C3 and anti-C5 Fab' antibody fragments to block monocyte spreading. It was found that anti-C5 Fab' inhibited by up to 100% the 3-h human monocyte spreading reaction induced by Bb; in contrast, anti-C3 Fab' or anti-C4 Fab' inhibited by less than 10%. That the inhibitory effect of anti-C5 Fab' was exerted directly on the monocyte was established when it was found that the 3-h monocyte spreading reaction was significantly inhibited by pretreating monocytes with anti-C5 Fab' for 20 min and then washing before the addition of Bb. The specificity of the inhibitory effect of anti-C5 Fab' was established by quantitatively absorbing the antibody fragments with polyacrylamide gel-purified C5 antigen: greater than 4 microgram of C5 absorbed by 100% the inhibitory activity of 10-20 microgram of anti-C5 Fab'. That factor Bb exerted its effect on monocytes by interacting directly with cell surface C5 was indicated when it was found that purified C5 inhibited the monocyte spreading reaction induced by Bb; greater than 25 microgram of C5 inhibited by 100% the spreading reaction induced by 3 microgram factor Bb.

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Role of Complement in Protection against Cryptococcus gattii Infection

Infection and Immunity ◽

10.1128/iai.01119-08 ◽

2008 ◽

Vol 77 (3) ◽

pp. 1061-1070 ◽

Cited By ~ 19

Author(s):

Kileen L. Mershon ◽

Alex Vasuthasawat ◽

Gregory W. Lawson ◽

Sherie L. Morrison ◽

David O. Beenhouwer

Keyword(s):

Complement Activation ◽

Alternative Pathway ◽

Complement Pathway ◽

Wild Type ◽

Complement Components ◽

Factor B ◽

Alternative Pathway Of Complement ◽

Deficient Mice

ABSTRACT Previous studies have shown that the alternative pathway of complement activation plays an important role in protection against infection with Cryptococcus neoformans. Cryptococcus gattii does not activate the alternative pathway as well as C. neoformans in vitro. The role of complement in C. gattii infection in vivo has not been reported. In this study, we used mice deficient in complement components to investigate the role of complement in protection against a C. gattii isolate from an ongoing outbreak in northwestern North America. While factor B-deficient mice showed an enhanced rate of death, complement component C3-deficient mice died even more rapidly, indicating that the alternative pathway was not the only complement pathway contributing to protection against disease. Both C3- and factor B-deficient mice had increased fungal burdens in comparison to wild-type mice. Histopathology revealed an overwhelming fungal burden in the lungs of these complement-deficient mice, which undoubtedly prevented efficient gas exchange, causing death. Following the fate of radiolabeled organisms showed that both factor B- and C3-deficient mice were less effective than wild-type mice in clearing organisms. However, opsonization of C. gattii with complement components was not sufficient to prolong life in mice deficient in complement. Killing of C. gattii by macrophages in vitro was decreased in the presence of serum from factor B- and C3-deficient versus wild-type mice. In conclusion, we have demonstrated that complement activation is crucial for survival in C. gattii infection. Additionally, we have shown that the alternative pathway of complement activation is not the only complement pathway contributing to protection.

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Novel Evidence That Alternative Pathway of Complement Cascade Activation is Required for Optimal Homing and Engraftment of Hematopoietic Stem/progenitor Cells

Stem Cell Reviews and Reports ◽

10.1007/s12015-021-10318-4 ◽

2022 ◽

Author(s):

Mateusz Adamiak ◽

Andrzej Ciechanowicz ◽

Vira Chumak ◽

Kamila Bujko ◽

Janina Ratajczak ◽

...

Keyword(s):

Progenitor Cells ◽

Purinergic Signaling ◽

Alternative Pathway ◽

Sterile Inflammation ◽

Complement Cascade ◽

Hematopoietic Stem ◽

Alternative Pathway Of Complement ◽

Endothelial Migration ◽

Lethal Irradiation

AbstractWe reported in the past that activation of the third (C3) and fifth element (C5) of complement cascade (ComC) is required for a proper homing and engraftment of transplanted hematopoietic stem/progenitor cells (HSPCs). Since myeloablative conditioning for transplantation triggers in recipient bone marrow (BM) state of sterile inflammation, we have become interested in the role of complement in this process and the potential involvement of alternative pathway of ComC activation. We noticed that factor B deficient mice (FB-KO) that do not activate properly alternative pathway, engraft poorly with BM cells from normal wild type (WT) mice. We observed defects both in homing and engraftment of transplanted HSPCs. To shed more light on these phenomena, we found that myeloablative lethal irradiation conditioning for transplantation activates purinergic signaling, ComC, and Nlrp3 inflammasome in WT mice, which is significantly impaired in FB-KO animals. Our proteomics analysis revealed that conditioned for transplantation lethally irradiated FB-KO compared to normal control animals have lower expression of several proteins involved in positive regulation of cell migration, trans-endothelial migration, immune system, cellular signaling protein, and metabolic pathways. Overall, our recent study further supports the role of innate immunity in homing and engraftment of HSPCs. Graphical Abstract

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