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Alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function

A novel component of the properdin system has been discribed which represents a heretofore unrecognized human serum protein. The protein has been tentatively termed the initiating factor (IF) because it functions in the initial reaction of the properdin pathway. IF is a 170,000 dalton beta-pseudoglo...

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Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1976
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2190422/
https://www.ncbi.nlm.nih.gov/pubmed/62010
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collection PubMed
description A novel component of the properdin system has been discribed which represents a heretofore unrecognized human serum protein. The protein has been tentatively termed the initiating factor (IF) because it functions in the initial reaction of the properdin pathway. IF is a 170,000 dalton beta-pseudoglobulin which is composed of two presumably identical 85,000 dalton chains linked by disulfide bonds. The protein reacts with antibody to nephritic factor, which is defined by its activity and is found in the serum of patients with certain nephritides. The activity of IF is heat stable. Upon treatment of serum with activators of the alternative pathway, the initial C3 convertase is assembled from IF, Factors D and C, C3, and magnesium without participation of properdin. It is the function of the enzyme to deposit C3b on the surface of the activator particles, thereby affording generation of the solid phase enzymes of the pathway, a process that is a prerequisite for properdin activation. By exposure to low pH, IF assumed the electrophoretic mobility of psi-globulin and acquired the ability to generate without activators a fluid phase C3 convertase in serum. Serum depleted of IF did not allow activation of the properdin pathway. Serum depleted of properdin did permit activation of the pathway and expression of cytolytic activity. These results raise the possibility that IF represents the recognition unit of the pathway.
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spelling pubmed-21904222008-04-17 Alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function J Exp Med Articles A novel component of the properdin system has been discribed which represents a heretofore unrecognized human serum protein. The protein has been tentatively termed the initiating factor (IF) because it functions in the initial reaction of the properdin pathway. IF is a 170,000 dalton beta-pseudoglobulin which is composed of two presumably identical 85,000 dalton chains linked by disulfide bonds. The protein reacts with antibody to nephritic factor, which is defined by its activity and is found in the serum of patients with certain nephritides. The activity of IF is heat stable. Upon treatment of serum with activators of the alternative pathway, the initial C3 convertase is assembled from IF, Factors D and C, C3, and magnesium without participation of properdin. It is the function of the enzyme to deposit C3b on the surface of the activator particles, thereby affording generation of the solid phase enzymes of the pathway, a process that is a prerequisite for properdin activation. By exposure to low pH, IF assumed the electrophoretic mobility of psi-globulin and acquired the ability to generate without activators a fluid phase C3 convertase in serum. Serum depleted of IF did not allow activation of the properdin pathway. Serum depleted of properdin did permit activation of the pathway and expression of cytolytic activity. These results raise the possibility that IF represents the recognition unit of the pathway. The Rockefeller University Press 1976-10-01 /pmc/articles/PMC2190422/ /pubmed/62010 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
spellingShingle Articles
Alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function
title Alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function
title_full Alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function
title_fullStr Alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function
title_full_unstemmed Alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function
title_short Alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function
title_sort alternative pathway of complement: demonstration and characterization of initiating factor and its properdin-independent function
topic Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2190422/
https://www.ncbi.nlm.nih.gov/pubmed/62010