MARCO expression on pediatric alveolar macrophages

Abstract

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.