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Updated: Aug 23, 2026
Isolation and In Vitro Culture of Murine and Human Alveolar Macrophages
Published on: April 20, 2018
MARCO expression on pediatric alveolar macrophages
Hazel J Bunn1, Lester Kobzik, Jonathan Grigg
1Department of Child Health, University of Leicester, Leicester, United Kingdom.
Background:
Phagocytosis of unopsonized pollutant particles by alveolar macrophages (AM) occurs via the macrophage receptor with collagenous structure (MARCO). In a previous study, we demonstrated that the laser scanning cytometer (LSC) can be used to characterize receptor expression in pediatric AM. Since we have demonstrated the presence of ultrafine carbon particles within AM obtained from young infants, we sought to determine MARCO expression by pediatric AM using the LSC, hypothesizing that MARCO expression, and hence the ability to phagocytize pollutant particles, is mature in early infancy.
Methods:
AM from 17 healthy children undergoing elective surgery, between 0.1 and 14.1 years of age, were obtained by bronchoalveolar lavage. Cytocentrifuged AM were dual immunostained with monoclonal antibodies to the panmacrophage marker CD68, and either MARCO or an appropriate isotypic control. Expression of MARCO was quantified using LSC and adjusted for cell area. Intensity of immunostaining was compared to each child's own isotypic control.
Results:
MARCO was present on 98% of pediatric AM. There was no association between age and either intensity of MARCO expression or the proportion of cells expressing MARCO.
Conclusions:
We conclude that there is no developmental immaturity in the major receptor responsible for unopsonized particle uptake in healthy young children.
Insights
Pediatric alveolar macrophages (AM) express the pollutant-clearing receptor MARCO (macrophage receptor with collagenous structure) early in life. This suggests pollutant particle uptake is mature in infants and young children.
Area of Science:
- Immunology
- Pediatric Pulmonology
- Environmental Health
Background:
- Alveolar macrophages (AM) phagocytose unopsonized particles via the macrophage receptor with collagenous structure (MARCO).
- Previous studies showed laser scanning cytometry (LSC) can characterize receptor expression in pediatric AM.
- Ultrafine carbon particles have been found in AM from infants, indicating potential exposure.
Purpose of the Study:
- To determine MARCO expression in pediatric AM using LSC.
- To test the hypothesis that MARCO expression is mature in early infancy.
- To assess the phagocytic capacity for pollutant particles in young children.
Main Methods:
- Bronchoalveolar lavage was used to obtain AM from 17 healthy children (0.1–14.1 years).
- AM were dual immunostained for CD68 (panmacrophage marker) and MARCO or an isotype control.
- MARCO expression was quantified using LSC, adjusted for cell area, and compared to isotype controls.
Main Results:
- MARCO was detected on 98% of pediatric AM.
- No association was found between age and MARCO expression intensity.
- No correlation was observed between age and the proportion of MARCO-expressing cells.
Conclusions:
- Pediatric AM express MARCO, the primary receptor for unopsonized particle uptake, early in life.
- There is no evidence of developmental immaturity in MARCO expression in healthy young children.
- The capacity for phagocytosing pollutant particles appears to be mature in early infancy.
