Figure 2

Postnatal structural and functional lung maturation in the mouse. Representative photomicrographs of postnatal lung histology, immunofluorescence macrophage localisation and respiratory trace patterns at P5 (A,F,K), P7 (B,G,L), P14 (C,H,M), P21 (D,I,N) and 3 months (E,J,O). Structural maturation (A-E) is demonstrated by a reduction in alveoli (a) size through the formation of new secondary septae (*) and a thinning of alveolar walls (arrows). Structural maturation accompanies functional maturation as indicated by deeper, more even respiratory trace patterns (K-O), which was quantified through waveform analysis (P-T). Postnatal lung development is accompanied by significant numbers of CSF-1R+ cells (green), which are predominantly macrophages (arrows) as indicated by F4/80 co-expression (red; F-J;). n=4 littermates/time point. ‘a’ represents significant difference compared to P5, ‘b’ compared to P7, ‘c’ compared to P11, ‘d’ compared to P14, ‘e’ compared to P21. Asterisks following letters represent level of significance, where *=p<0.05, **=p<0.01, ***=p<0.001.