Fig. 7. Donor bone-marrow-derived cells (blue) in recipient bleomycin-injured lungs 1 and 2.5 days after injection. (A,B) Ovoid donor cells against a pulmonary blood vessel wall (arrow; A) and in the injured lung parenchyma (arrow; B) 1 day after injection. (C,D) By 2.5 days, donor-derived cells can be found in the lung parenchyma as elongated cells (arrows) with attenuated cytoplasmic extensions (arrowheads). As shown in A-D, engrafted cells do not exhibit the location and shape of type II cells. (E) Phase microscopy of D demonstrating that engrafted cells do not contain lamellar bodies. For comparison, two neighboring endogenous type II cells (lacZ negative; open arrows) with characteristic lamellar bodies are shown. (F) PCNA immunostained lung section with a blue donor-derived cell 2.5 days after injection. This nucleus (arrow) does not stain for proliferating cell nuclear antigen (PCNA, brown). In contrast, a neighboring lacZ-negative cell stains positively for PCNA (open arrow; nuclei counter stained purple with Haematoxylin).