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Published on: May 31, 2018
Apoptotic cell-mediated immunoregulation of dendritic cells does not require iC3b opsonization
Edward M Behrens1, Yue Ning, Nidal Muvarak
1Laboratory of Dendritic Cell Biology, Division of Rheumatology, Joseph Stokes, Jr. Research Institute, Children's Hospital of Philadelphia, Philadelphia, PA 19104-4318, USA. behrens@email.chop.edu
Complement receptor 3 (CR3) engagement by apoptotic cells does not suppress dendritic cell (DC) immune responses. CR3 interaction is dispensable for the anti-inflammatory effects of apoptotic cells on DCs.
Area of Science:
- Immunology
- Cell Biology
- Dendritic Cell Function
Background:
- Recent studies suggest CR3 activation on dendritic cells (DCs) suppresses TLR-induced TNF-alpha and IL-12 production.
- This immune suppression is proposed to result from CR3 recognition of iC3b opsonized apoptotic cells.
- Previous investigations utilized artificial ligands to activate CR3.
Purpose of the Study:
- To investigate if iC3b opsonized apoptotic cells induce similar suppressive changes as artificial CR3 ligands.
- To explore the kinetics of iC3b opsonization in murine models of apoptosis.
- To determine the role of CR3 engagement in mediating the anti-inflammatory effects of apoptotic cells on DCs.
Main Methods:
- Investigated iC3b opsonization kinetics in gamma-irradiated thymocytes and IL-3-deprived BaF3 cells.
- Utilized homogenous populations of early apoptotic cells (IL-3 deprived BaF3 cells).
- Assessed TLR-induced cytokine production (TNF-alpha, IL-12, IL-10) and phagocytosis by bone marrow-derived DCs.
Main Results:
- iC3b opsonized apoptotic cells engage CR3 on DCs, but this interaction is dispensable for anti-inflammatory effects.
- Apoptotic cells heterogeneously inhibit TLR-induced TNF-alpha and IL-12 production by DCs.
- Apoptotic cells induce homogeneous IL-10 production, but it's not essential for TNF-alpha and IL-12 inhibition.
- iC3b opsonization does not significantly impact apoptotic cell ingestion by DCs.
Conclusions:
- The apoptotic cell receptor system on DCs is redundant.
- Absence of CR3 engagement does not significantly affect the normal anti-inflammatory processing of apoptotic cells by DCs.
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