Migrating lung monocytes internalize and inhibit growth of Aspergillus fumigatus conidia

Abstract Monocytes are important players to combat ubiquitously present fungus Aspergillus fumigatus. Recruitment of monocytes to sites of fungal infection was shown in vivo, and purified murine and human blood monocytes are able to induce inflammatory and fungicidal mediators as well as the host cell and the fungal transcriptional responses upon exposure to A.fumigatus. Mononuclear tissue phagocytes are phenotypically and functionally different from those circulating in the blood and their role in antifungal defences is much less understood. In this study, we identified a population of migrating CD43+ monocytes in cells isolated from rat distal lungs. These cells phenotypically different from alveolar macrophages, showed clearly distinct locomotory behaviour on the surface of primary alveolar cells resembling previously described endothelial patrolling. The CD43+ monocytes internalized live A.fumigatus conidia resulting in inhibition of conidial germination and hyphal growth. Thus, migrating lung monocytes might play an important role in local defence against pulmonary pathogens.