As the 3 days post-infection (3 d p.i.), 7 d p.i. and 14 d p.i. represent different infectious periods, the lungs were harvested, and increased expression levels of Fcgr1 mRNA were detected as the infection progressed (Figure 1A), indicating the involvement of FcγRI in response to chlamydial infection. Here, FCGR1A is linked to infection.