Fig. 4

CD74 expression in AT2 cells. a Live single cells were stained for CD74. Compared to controls (left), only a small fraction of EpCAM⁺ cells were positive for CD74 expression (middle and right). b CD74 staining was performed before fixation and permeabilization of single lung cells (surface staining). EpCAM⁺ cells were identified (top, left), and proSP-C⁺ cells (top, middle) were analyzed for CD74 expression (top, right). proSP-C⁺ cells showed uniform but weak CD74 expression. A small fraction of proSP-C⁺ cells expressed CD74 at higher levels than others (bottom, right) when compared to controls (bottom, left). c CD74 staining was performed after the fixation and permeabilization of single lung cells (intracellular staining). EpCAM⁺ cells were identified (top, left), and proSP-C⁺ cells (top, middle) were analyzed for CD74 expression (top, right. Bottom). High CD74 expression was observed (bottom, right and left) in proSP-C⁺ cells. EpCAM, epithelial cell adhesion molecule; proSP-C, pro-surfactant protein C; SSC, side scatter; PE, phycoerythrin; APC, allophycocyanin; FITC, fluorescein isothiocyanate