The type 1 alveolar lining cells of the mammalian lung. I. Isolation and enrichment from dissociated adult rabbit lung.

With removal of large numbers of macrophages by airway lavage, Type 1 cells were isolated in heterogeneous cell populations following the stepwise dissociation of lung tissue. Using a carefully timed collagenase-trypsin digestive sequence at 37 C, unwanted cellular and noncellular lung components were minimized prior to selective release of Type 1 cells. Resulting heterogeneous cell suspensions containing well-preserved Type 1 cells, as determined by electron microscopy, were layered onto a shallow gradient (3 to 6% Ficoll in minimal essential medium [MEM]) and separated at unit gravity into enriched subpopulations of various cell types. These included various fractions enriched with respect to Type 1 cells (70%), Type 2 cells (82%), and macrophages (81%). Identification of Type 1 cells following their isolation and gradient enrichment was established by light microscopic staining techniques and by specific cell surface characteristics in vitro as visualized by electron microscopy.