Immune Defense Protein Expression in Highly Purified Mouse Lung Epithelial Cells

Lung epithelial cells play critical roles in initiating and modulating immune responses during pulmonary infection or injury. To better understand the spectrum of immune response–related proteins present in lung epithelial cells, we developed an improved method of isolating highly pure primary murine alveolar type (AT) II cells and murine tracheal epithelial cells (mTECs) using negative selection for a variety of lineage markers and positive selection for epithelial cell adhesion molecule (EpCAM), a pan-epithelial cell marker. This method yielded 2–3 × 106 ATII cells/mouse lung and 1–2 × 104 mTECs/trachea that were highly pure (>98%) and viable (>98%). Using these preparations, we found that both ATII cells and mTECs expressed the Lyn tyrosine kinase, which is best studied as an inhibitory kinase in hematopoietic cells. However, we found little or no expression of Syk in either ATII cells or mTECs, which is in contrast to earlier published reports. Both cell types expressed C-type lectin receptors, anaphy...