Abstract

BackgroundIt has been reported that C-reactive protein (CRP) binds both leukocyte FcγRIIA (CD32) and the plasma membrane of apoptotic cells. Since FcγRIIA becomes functionally enabled during neutrophil apoptosis, we sought to determine whether CRP bound to apoptotic neutrophils via FcγRIIA.MethodsWe prepared directly labelled CRP and demonstrated that it was essentially free of IgG. We looked for evidence of CRP binding to intact, membrane impermeable apoptotic human neutrophils and to FcγRIIA-transfected Jurkat cells. We examined the functional consequences of incubation with CRP upon phagocytosis of apoptotic cells by human monocyte-derived macrophages.ResultsWe could not detect binding of purified soluble CRP to classical early apoptotic human neutrophils or to FcγRIIA-transfected Jurkat cells. In contrast, membrane-permeable late apoptotic neutrophils exhibited strong CRP binding, which comprised both Ca2+-dependent and heparin-inhibitable Ca2+-independent components. However, there was no effect of CRP binding upon phagocytosis of late apoptotic neutrophils by macrophages.ConclusionPotential apoptotic cell opsonins such as CRP may bind only to intracellular structures in cells with leaky membranes that have progressed to a late stage of apoptosis.

Highlights

  • It has been reported that C-reactive protein (CRP) binds both leukocyte FcγRIIA (CD32) and the plasma membrane of apoptotic cells

  • Native CRP and Fluorescein isothiocyanate (FITC)-CRP migrated as single bands when examined by SDS-PAGE (Figure 1a)

  • FITC-CRP was shown to be functionally active by demonstrating Ca2+-dependent binding to phosphorylcholine-coated beads (Figure 1c)

Read more

Summary

Introduction

It has been reported that C-reactive protein (CRP) binds both leukocyte FcγRIIA (CD32) and the plasma membrane of apoptotic cells. Since FcγRIIA becomes functionally enabled during neutrophil apoptosis, we sought to determine whether CRP bound to apoptotic neutrophils via FcγRIIA. We have recently reported that IgG-containing immune complexes bound preferentially to functionally enabled FcγRIIA (CD32) on apoptotic neutrophils [3,4]. It has been proposed that FcγRIIA is a receptor for the pentraxin C-reactive protein (CRP) [5,6], serum concentrations of which may increase more than 1000-fold during acute inflammation [7,8]. In the present study we sought to determine whether binding of CRP to apoptotic neutrophils was (page number not for citation purposes)

Methods
Results
Discussion
Conclusion

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.