The scholarly study protocol, like the statistical analysis plan, is offered by NEJM.org. All the authors had access to all the data and vouch for the accuracy and completeness of the info and for the fidelity of the trial to the final process. The sponsor executed the data analyses. The original manuscript was drafted by the initial two authors. All of the authors were involved in the interpretation of the data and in the composing and editing of the manuscript with support from a professional medical writer funded by Amgen. Laboratory Procedures The allergen for inhalation was selected based on results from skin-prick testing.This specific home of hematopoietic stem cells can be used in medical bone marrow transplantation also, where diseased blood cells – for example leukemic cells – are changed by healthy cells. However, the limited amount of donor stem cells which may be tolerated by the recipient is still an extremely high hurdle for the achievement of such a stem cell transplantation. This is why better understanding of the function of stem cells in the body is still of particular importance to become in a position to find solutions for this problem. In contrast, it remained unknown if the length of specific cell division phases regulates the behavior of hematopoietic stem cells.