Size-dependent particle uptake and trafficking by antigen presenting cells in different anatomical respiratory tract compartments

Abstract

Effects of biomedical particles on lung antigen presenting cells (APC) such as dendritic cells (DC) and alveolar macrophages (AM) remain poorly understood to date.

BALB/c mice intra-nasally received different sized (20nm, 50nm, 100nm, 200nm, 1000nm) fluorescent polystyrene particles. Two and 24h after instillation, FACS and confocal microscopy were performed on main conducting airways lung parenchyma, lung draining lymph nodes (LDLN) and BALF to analyse particle uptake in CD11b-/CD103+ DC and AM.

In airways, frequencies of particle+ DC 24h after exposure were higher for 20nm particles compared to 1000nm particles (12.0±3.2% vs. 1.220 ± 0.3%; p=0.0283). At 24 hours, in lung parenchyma DC, preferential uptake of 20nm (43.5±3.5%, p=0.0001) and 50nm particles (36.2±0.4%, p<0.0001) occurred, compared to 1000nm particles (9.700 ± 0.9%). These changes mirrored LDLN, where DC preferentially trafficked 20nm (17.8±2.3%, p=0.0038) and 50nm particles (20.4±1.2%, p< 0.0001) compared to 1000nm particles (3.477±0.8%). AM ingested all sizes with a preference for, smaller particles (20nm: 88.0±1.8%, p=0.0001; 50nm: 8.6±0.5 79.5±1.2%, p<0.0001; 100nm: 69.2±2.1%, p=0.0041; 200nm: 61.5±2.1%, p=0.0361; 1000nm: 53.72±1.5%) 24h after exposure. Following uptake, DC up regulated expression of CD40 and CD86 independently of particle size. Confocal microscopy confirmed uptake and size distribution in AM and DC in situ.

Particle size is a key factor determining uptake and trafficking from the lung to LDLN. This has important consequences on downstream immunological effects of both ambient inhaled particles and novel carriers for pulmonary delivery of drugs or vaccines.