Fig 2: BPIFA1 is genotype dependently differentially expressed in the distal trachea in acute murine S. aureus pneumonia. BPIFA1 protein expression was examined in the distal trachea from PBS-treated mice and mice infected with S. aureus 48 h after infection. a BPIFA1 immunohistochemistry of representative sections and b percentage of BPIFA1-positive cells per 100 µm basement membrane of the distal trachea of Clca1-/- mice compared to WT mice at 48 h post-infection. Bar 10 µm. *p < 0.05 vs. WT; #p < 0.05 vs. PBS controls. n = 4 per group

Fig 3: BPIFA1 is expressed in murine alveolar macrophages. Immunohistochemistry of murine lung sections with anti-BPIFA1 antibody (DAB, brown, left image), anti-CD68 antibody (NF, red, middle image), and double staining (right image). Bar 50 µm; bar inset 20 µm

Fig 4: Bpifa1 expression was decreased in murine WT but not Clca1-/- tracheal tissue in S. aureus pneumonia. Bpifa1 expression was determined via qRT-PCR in Clca1-/- and WT tracheal and lung tissue from a murine model of acute pneumonia 12 and 24 h post-infection with S. aureus. Dotted lines indicate fold changes of 0.5 and 2 as limits for valid statement of lowered or elevated parameters, respectively. Ct cycle threshold. *p < 0.05 vs. WT, ##p < 0.01 vs. PBS controls. n = 8–11 per group