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Enhanced phagocytosis in neonatal monocyte-derived macrophages is associated with impaired SHP-1 signaling
Donald W Lawrence1, Joyce M Koenig
1Department of Pediatrics, Division of Neonatology, Saint Louis University School of Medicine, Saint Louis, MO, USA.
Abstract:
Resident macrophages represent a first line of defense through the ingestion of microbial pathogens. Phagocytosis mediated by immunoglobulin-binding Fc receptors is a complex series of events involving tyrosine phosphorylation and dephosphorylation. In the present study we determined that the phagocytic capacity of neonatal monocyte-derived macrophage (MDM) was enhanced in comparison to adult MDM. Cross-linking of surface FcγRIIa receptors enhanced tyrosine phosphorylation of several proteins in both groups, followed by a reduction in tyrosine phosphorylation in adult but not neonatal MDM. Expression of the tyrosine phosphatase SHP-1 was similar in neonatal and adult MDM; however, baseline SHP-1 activity levels were diminished in neonatal MDM. Cross-linking of FcγRIIa receptors induced a greater increase in SHP-1 activity in adult MDM vs. neonatal MDM. The cytoplasmic adapter protein Cbl is a SHP-1 ligand and negatively affects phagocytosis. As determined by co-immunoprecipitation assays, SHP-1 and Cbl did not associate to the same extent in neonatal as compared to adult MDM. Our data suggest that the enhanced phagocytic capacity of neonatal MDM is associated with decreased SHP-1 activity and alteration of downstream signaling pathways.
Insights
Neonatal macrophages exhibit enhanced phagocytosis compared to adult macrophages. This is linked to reduced tyrosine phosphatase SHP-1 activity and altered downstream signaling pathways in neonatal immune cells.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Resident macrophages are crucial for innate immunity, engulfing pathogens via Fc receptor-mediated phagocytosis.
- Phagocytosis involves intricate tyrosine phosphorylation and dephosphorylation signaling cascades.
Purpose of the Study:
- To compare the phagocytic capacity of neonatal and adult monocyte-derived macrophages (MDMs).
- To investigate the role of tyrosine phosphatase SHP-1 and its interaction with Cbl in neonatal MDM phagocytosis.
Main Methods:
- Comparative analysis of phagocytic activity in neonatal and adult MDMs.
- FcγRIIa receptor cross-linking to assess tyrosine phosphorylation.
- Measurement of SHP-1 expression and activity.
- Co-immunoprecipitation assays to study SHP-1 and Cbl association.
Main Results:
- Neonatal MDMs demonstrated enhanced phagocytic capacity compared to adult MDMs.
- FcγRIIa cross-linking induced sustained tyrosine phosphorylation in neonatal MDMs but transient phosphorylation in adults.
- Neonatal MDMs exhibited lower baseline SHP-1 activity and a reduced increase in SHP-1 activity post-stimulation compared to adults.
- SHP-1 and Cbl association was weaker in neonatal MDMs than in adult MDMs.
Conclusions:
- Enhanced phagocytosis in neonatal MDMs is associated with diminished SHP-1 phosphatase activity.
- Altered downstream signaling, including reduced SHP-1/Cbl interaction, contributes to the superior phagocytic function of neonatal macrophages.
