Figure 2.

Hematopoietic reconstitution by a single GFP+ bone marrow stem cell. A single hematopoietic stem cell was purified from the bone marrow of a B-actin–GFP donor mouse, and 1 yr later recipient blood and lung tissue were harvested for analysis. (A) FACS histogram illustrates robust hematopoietic reconstitution of 79% of the recipient's peripheral blood with donor-derived GFP+ cells. (B) FACS-analysis of live cells (PI-negative) from the left lung of this recipient, shows the presence of GFP+ marrow-derived cells (25% of the lung cell suspension). (C) FACS-analysis of the GFP+ and GFP(−) subgates of the lung cell suspension from B demonstrates that 99% of the GFP+ cells (green histogram) express the panhematopoietic marker CD45. In contrast, 22% of GFP(−) cells in this sample are CD45+ (black histogram). An aliquot of this sample stained with a negative control antibody of identical isotype illustrates specificity of the CD45 antibody staining (purple histogram). Similar engraftment results were obtained from recipients that received either unfractionated marrow or 200 purified HSC transplants. (D) A frozen tissue section prepared from the right lung of this recipient was immunostained with Cy3-conjugated anti–pro-SP-C antibody showing that AT2 cells (red) and donor marrow–derived cells (green) are distinct, with the possible artifactual exception of two cells whose tips appear to overlap (arrow).