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Quantification of the pro-form of human complement component factor D (adipsin)

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  • Maiken Lumby Henriksen, Clinical Cell Biology, Research Unit of Pathology, Department of Clinical Research, University of Southern Denmark and Department of Pathology, Odense University Hospital, Odense, Denmark; Department of Molecular Medicine, University of Southern Denmark, Odense, Denmark; Clinical Cell Biology, Vejle Hospital - Lillebælt Hospital, University of Southern Denmark, Vejle, Denmark; Department of Forensic Medicine, Aarhus University, Aarhus, Denmark. Electronic address: thomas.levin.andersen@rsyd.dk.
  • ,
  • Christian Nielsen, Syddansk Universitet
  • ,
  • Dennis Pedersen
  • Gregers Rom Andersen
  • Steffen Thiel
  • Yaseelan Palarasah, Clinical Cell Biology, Research Unit of Pathology, Department of Clinical Research, University of Southern Denmark and Department of Pathology, Odense University Hospital, Odense, Denmark; Department of Molecular Medicine, University of Southern Denmark, Odense, Denmark; Clinical Cell Biology, Vejle Hospital - Lillebælt Hospital, University of Southern Denmark, Vejle, Denmark; Department of Forensic Medicine, Aarhus University, Aarhus, Denmark. Electronic address: thomas.levin.andersen@rsyd.dk.
  • ,
  • Soren Werner Karlskov Hansen, Clinical Cell Biology, Research Unit of Pathology, Department of Clinical Research, University of Southern Denmark and Department of Pathology, Odense University Hospital, Odense, Denmark; Department of Molecular Medicine, University of Southern Denmark, Odense, Denmark; Clinical Cell Biology, Vejle Hospital - Lillebælt Hospital, University of Southern Denmark, Vejle, Denmark; Department of Forensic Medicine, Aarhus University, Aarhus, Denmark. Electronic address: thomas.levin.andersen@rsyd.dk.

Factor D (also known as adipsin) is a serine protease and part of the complement system, involved in innate immune responses and effector functions of antibodies. Factor D cleaves factor B complexed with C3b, leading to the C3 convertase C3bBb. This C3 convertase is central in the alternative activation pathway and the amplification loop, which amplifies the two other complement activation pathways: the classical pathway and the lectin pathway. Adipocytes synthesize factor D as a pro-form comprising 6 additional residues that must be cleaved off to generate a mature form. The MBL-associated serine protease 3 (MASP-3), found in complex with the pattern recognition molecules of lectin activation pathway, converts the pro-form to mature factor D, which reportedly is the most abundant form found in the circulation at concentrations of 1-2 μg/ml among healthy individuals. The mature factor D is rate-limiting for complement activation, but little is known about the distribution of pro vs. mature factor D in the circulation, the regulation hereof and the potential activation stimuli of the lectin pathway, responsible for activation of MASP-3 and subsequent conversion of pro-form of factor D. In this light we established and validated an ELISA specific for measuring the pro-form of complement factor D. With a working range of 0.82-25 ng/ml, acceptable intra and inter assay CVs, and a relative recovery rate above 90%, we found that the median plasma concentration in Danish blood donors was 134 ng/ml; corresponding to that 8-15% factor D circulates as pro-form. We also found that blood sampling procedures affect conversion and hence the levels measured in serum and plasma.

OriginalsprogEngelsk
TidsskriftJournal of Immunological Methods
Vol/bind507
Sider (fra-til)113295
ISSN0022-1759
DOI
StatusE-pub ahead of print - 6 jun. 2022

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Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.

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