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Properdin and factor H: opposing players on the alternative complement pathway "see-saw"

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posted on 2016-01-26, 13:46 authored by L. Kouser, M. Abdul-Aziz, A. Nayak, Cordula M. Stover, R. B. Sim, U. Kishore
Properdin and factor H are two key regulatory proteins having opposite functions in the alternative complement pathway. Properdin up-regulates the alternative pathway by stabilizing the C3bBb complex, whereas factor H downregulates the pathway by promoting proteolytic degradation of C3b. While factor H is mainly produced in the liver, there are several extrahepatic sources. In addition to the liver, factor H is also synthesized in fetal tubuli, keratinocytes, skin fibroblasts, ocular tissue, adipose tissue, brain, lungs, heart, spleen, pancreas, kidney, muscle, and placenta. Neutrophils are the major source of properdin, and it is also produced by monocytes, T cells and bone marrow progenitor cell line. Properdin is released by neutrophils from intracellular stores following stimulation by N-formyl-methionine-leucine-phenylalanine (fMLP) and tumor necrosis factor alpha (TNF-α). The HEP G2 cells derived from human liver has been found to produce functional properdin. Endothelial cells also produce properdin when induced by shear stress, thus is a physiological source for plasma properdin. The diverse range of extrahepatic sites for synthesis of these two complement regulators suggests the importance and need for local availability of the proteins. Here, we discuss the significance of the local synthesis of properdin and factor H. This assumes greater importance in view of recently identified unexpected and novel roles of properdin and factor H that are potentially independent of their involvement in complement regulation.

History

Citation

Frontiers in Immunology, 2013, 4 : 93 (12)

Author affiliation

/Organisation/COLLEGE OF MEDICINE, BIOLOGICAL SCIENCES AND PSYCHOLOGY/School of Medicine/Department of Infection, Immunity and Inflammation

Version

  • VoR (Version of Record)

Published in

Frontiers in Immunology

Publisher

Frontiers

issn

1664-3224

Acceptance date

2013-04-05

Copyright date

2013

Available date

2016-01-26

Publisher version

http://journal.frontiersin.org/article/10.3389/fimmu.2013.00093/abstract

Language

en

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