Immunophenotyping of bone marrow-derived eosinophils in respiratory pathogen infections (INC2P.421)

Abstract

Abstract Asthmatic individuals are considered at high risk of developing viral and bacterial infections. Since eosinophils are abundant in the airways of allergic asthmatics, we hypothesized eosinophils were susceptible to infection by common respiratory pathogens associated with pneumonia. We used bone marrow-derived eosinophils (BMdEos) to simulate exposure to Influenza A Virus (IAV) or Streptococcus pneumoniae. A subset of BMdEos and lung eosinophils exposed to IAV possessed surface-bound nucleoprotein when examined by flow cytometry, indicating both sources of eosinophils were infected with virus. BMdEos also upregulated MHCI and CD86, while MHCII and CD80 remained unchanged. Although microscopically BMdEos appeared homogeneous, two distinct populations based on Siglec-F expression were observed when phenotyped by flow cytometry. MHCI was upregulated almost exclusively by the Siglec-Fhi cells after IAV exposure. Conversely, BMdEos pulsed with S. pneumoniae upregulated MHCII, while downregulating MHCI. Although elevated MHCII was observed for both Siglec-F populations, Siglec-Fint cells upregulated MHCII levels when pulsed with fewer bacteria. Here, we showed that BMdEos can interact with both IAV and S. pneumoniae, responding divergently by modulating surface levels of MHC molecules. Furthermore, we propose the use of BMdEos as a viable in vitro system for examining eosinophils responses to respiratory pathogens.