Fig. 1

MHCII expression in murine AT2 cells. a Immunofluorescence analysis of cells from 9-wk.-old mice shows MHCII expression on proSP-C⁺ AT2 cells. Note that AT1 cells are negative for MHCII expression. Scale bars, 50 μm. b Representative FACS plots show that EpCAM⁺ cells were identified among CD45⁻CD31⁻ cells (top) and analyzed for proSP-C expression (bottom). c MHCII expression in proSP-C⁺ cells. The histogram shows that proSP-C⁺ cells express MHCII (left). Compared to control (middle), 99.0% of proSP-C+ cells are positive for MHCII expression (right). d MHCII expression in proSP-C⁻ cells. Histogram (left) and FACS plots (middle and right) show that the majority of proSP-C⁻ cells are negative for MHCII expression. e Representative FACS plot shows that EpCAM⁺ cells are classified into 3 subpopulations (P1, P2, and P3) based on EpCAM and MHCII expression (right) compared to control (left). f EpCAM^medMHCII⁺ cells (P1) (left) are positive for proSP-C expression. EpCAM^hiMHC⁻ cells (P2) (middle) and EpCAM^lowMHC⁻ cells (P3) (right) are negative for proSP-C expression. g Representative FACS plot shows that almost all P1 cells are positive for proSP-C expression (right) compared to controls (left). h EpCAM⁺proSP-C⁺ cells were back-gated to the plot of EpCAM and MHCII. Note that most proSP-C⁺ cells were in the P1 gate. AT1 cells, alveolar type 1 cells; AT2 cells, alveolar type 2 cells; EpCAM, epithelial cell adhesion molecule; MHCII, major histocompatibility complex II; proSP-C, pro-surfactant protein C; DAPI, 4′,6-diamidino-2-phenylindole; SSC, side scatter; PE, phycoerythrin; APC, allophycocyanin