Figure 4

Immunostaining of α ₅ nAChR subunits, proSP-C, T1α, CCSP, and FoxJ1 during the mid-saccular post natal period (PN1) and late saccular period (PN4) of lung development. α₅ (A, C) did not clearly co-localize with proSP-C expressing ATII cells (B) and was detected in some ATI cells stained with T1α (D, arrows) but not all (D, arrowhead). α₅ expression (E, G) was abundantly detected in the proximal lung as evidenced by co-expression by CCSP-expressing Clara cells (F, arrow) and ciliated cells in the proximal airways that express FoxJ1 (H, arrow). At PN4, α₅ (I, K) was co-expressed by ATII and ATI cells via co-localization with proSP-C (J, arrow) and T1α (L, arrow), respectively. PN4 was a period in which α₅ expression was nearly absent in the proximal lung, therefore co-localization with CCSP in Clara cells (N, arrowhead) and FoxJ1 in ciliated cells (P, arrowhead) was poor. Lung sections stained without primary antibodies were negative (not shown). All images are at 40X original magnification and scale bars represent 50 μm.