Isolation and characterization of equine nasal mucosal CD172a+ cells

The nasal mucosa surface is continuously confronted with a broad variety of environmental antigens, ranging from harmless agents to potentially harmful pathogens. This area is under rigorous control of professional antigen presenting cells (APCs), such as dendritic cells (DCs) and macrophages. Mucosal APCs play a crucial role in inducing primary immune responses and the establishment of an immunological memory. In the present study, a detailed characterization of CD172a⁺ cells, containing the APCs residing in the equine nasal mucosa was performed for the first time. CD172a⁺ cells were isolated from collagenase-treated equine nasal mucosa fragments by MACS. Expression of surface markers was determined by flow cytometry and functional analysis was done by measuring the uptake of FITC conjugated ovalbumin (FITC-OVA). Cell surface phenotype of the isolated cells was as follows: 90% CD172a⁺, 30% CD1c⁺, 46% CD83⁺, 42% CD206⁺ and 28% MHC II⁺. This clearly differs from the phenotype of blood-derived monocytes: 96% CD172a⁺, 4% CD1c⁺, 11% CD83⁺, 9% CD206⁺, 72% MHC II⁺ and blood monocyte derived DCs: 99% CD172a⁺, 13% CD1c⁺, 30% CD83⁺, 51% CD206⁺ and 93% MHC II⁺. The CD172a⁺ nasal mucosal cells were functionally able to endocytose FITC-OVA but to a lesser degree than monocyte-derived DCs. Together, these results demonstrate that the isolated CD172a⁺ nasal mucosal cells resemble immature DCs in the nasal area.