Stem cells can alternatively be derived from unrelated donor (allogeneic) and administered to a recipient to treat a variety of diseases. This strategy is used to treat certain forms of leukemia, for example. While potentially efficacious, using allogeneic stem cells presents greater complexity than the use of autologous stem cells because there is a risk of rejection, tumor growth or other unwanted sides effects including graft versus host disease. The use of allogeneic mesenchymal stem cells therapy was tested in a well-designed randomized clinical trial for subject who had moderate or severe COPD. Comprehensive studies using autologous mesenchymal stem cells to treat COPD are not yet available. The therapy was judged to be safe and well tolerated, an observation that has been made regarding the use of autologous stem cell therapy in other studies. However, there was no measurable difference after two years of follow-up in a variety of measures that characterize COPD, including an improvement in lung function (lung volume, spirometry, oxygenation and diffusion capacity), exercise capacity (6-minute walk distance), shortness of breath or quality of life in those who did or did not receive stem cells. There was a difference in the level of one marker of inflammation (C-reactive protein) in a subset of these patients, but no difference was observed in several other inflammatory markers when comparing the two groups.