Methods of in vitro macrophage maturation confer variable inflammatory responses in association with altered expression of cell surface dectin-1.

Macrophage differentiation and polarization occur in vivo under the influence of the localized cytokine milieu. In vitro studies frequently rely on cellular differentiation in culture; hence, unrecognized variables could have a large influence on the observed cellular phenotype. We measured macrophage in vitro responses to fungal ligands (Aspergillus germ tubes and zymosan), focusing on the degree to which culture conditions impact stimulatory responses through the C-type lectin receptor, dectin-1, which is involved in both MyD88-dependent and MyD88-independent signaling in response to fungal beta1,3 glucan.

Dectin-1 and TLRs permit macrophages to distinguish between different Aspergillus fumigatus cellular states.

Aspergillus fumigatus is a common cause of invasive and allergic pulmonary disease. Resting conidia of the filamentous fungus are constantly inhaled, but cause infection only after initiating hyphal growth. In this study, we have explored whether macrophages can distinguish between resting spores and the maturing, potentially invasive form of the fungus.