Related Experiment Video
Updated: May 26, 2026
Neonatal Mouse Bone Marrow Isolation and Preparation of Bone Marrow-Derived Macrophages
Published on: May 24, 2024
Impaired neonatal macrophage phagocytosis is not explained by overproduction of prostaglandin E2
Megan N Ballinger1, Marc Peters-Golden, Bethany B Moore
1Department of Internal Medicine, Division of Pulmonary and Critical Care Medicine, The University of Michigan, Ann Arbor, MI, USA. mnhender@umich.edu
Background:
Neonates and young infants manifest increased susceptibility to bacterial, viral and fungal lung infections. Previous work has identified a role for eicosanoids in mediating host defense functions of macrophages. This study examines the relationship between alveolar macrophage (AM) host defense and production of lipid mediators during the neonatal period compared to adult AMs.
Methods:
AMs were harvested from young (day 7 and day 14) and adult (~10 week) rats. The functionality of these cells was assessed by examining their ability to phagocytose opsonized targets, produce cytokines, eicosanoids and intracellular cAMP measured by enzyme immunoassays, and gene expression of proteins, enzymes and receptors essential for eicosanoid generation and phagocytosis measured by real time RT-PCR.
Results:
AMs from young animals (day 7 and 14) were defective in their ability to phagocytose opsonized targets and produce tumor necrosis factor (TNF)- α. In addition, young AMs produce more prostaglandin (PG) E(2), a suppressor of host defense, and less leukotriene (LT) B(4), a promoter of host defense. Young AMs express higher levels of enzymes responsible for the production of PGE(2) and LTB(4); however, there was no change in the expression of E prostanoid (EP) receptors or LT receptors. Despite the similar EP profiles, young AMs are more responsive to PGE(2) as evidenced by their increased production of the important second messenger, cyclic AMP. In addition, young AMs express higher levels of PDE3B and lower levels of PDE4C compared to adult AMs. However, even though the young AMs produced a skewed eicosanoid profile, neither the inhibition of PGE(2) by aspirin nor the addition of exogenous LTB(4) rescued the defective opsonized phagocytosis. Examination of a receptor responsible for mediating opsonized phagocytosis showed a significant decrease in the gene expression levels of the Fcgamma receptor in young (day 7) AMs compared to adult AMs.
Conclusion:
These results suggest that elevated production of PGE(2) and decreased production of LTB(4) do not contribute to impaired opsonized macrophage phagocytosis and highlight an important difference between young and adult AMs.
Insights
Neonatal rats have impaired alveolar macrophage (AM) function, producing more prostaglandin E(2) and less leukotriene B(4). This skewed eicosanoid profile does not explain the defective phagocytosis observed in young AMs.
Area of Science:
- Immunology
- Neonatal Research
- Macrophage Biology
Background:
- Neonates are highly susceptible to lung infections.
- Eicosanoids play a role in macrophage-mediated host defense.
- This study compares neonatal and adult rat alveolar macrophage (AM) function and lipid mediator production.
Purpose of the Study:
- To investigate the relationship between AM host defense and lipid mediator production in neonatal versus adult rats.
- To determine the functional capacity of neonatal AMs compared to adult AMs.
Main Methods:
- Harvested AMs from young (day 7, 14) and adult (~10 week) rats.
- Assessed phagocytosis, cytokine production, eicosanoid and cAMP levels via enzyme immunoassays.
- Measured gene expression of proteins, enzymes, and receptors using real-time RT-PCR.
Main Results:
- Young AMs showed defective phagocytosis and lower TNF-α production.
- Young AMs produced more PGE(2) (host defense suppressor) and less LTB(4) (host defense promoter).
- Defective phagocytosis was linked to decreased Fcgamma receptor gene expression in young AMs, not eicosanoid imbalance.
Conclusions:
- Elevated PGE(2) and decreased LTB(4) do not cause impaired phagocytosis in young AMs.
- Significant differences exist in young versus adult AM host defense mechanisms.
- Fcgamma receptor expression is a key factor in neonatal AM phagocytic deficiency.
