PTPRC and infection: In order to investigate the effects of CS exposure plus IAV/H3N2 infection on the polarization of pulmonary macrophages, alveolar macrophages (AMs) in BALF were defined by flow cytometry analysis based on the specific markers of M1 AMs (CD45+Siglec-F+CD11c+CD86+population) and M2 AMs (CD45+Siglec-F+CD11c+CD206+ population).