In this photo taken, April 12, 2011, stem cell recipient Jacob Kowalik, 7, and his father, Michael Kowalik, right listen to a nurse at Children's Memorial Hospital in Chicago as Jacob undergoes a ... more 
In this photo taken, April 12, 2011, stem cell recipient Jacob Kowalik, 7, and his father, Michael Kowalik, right listen to a nurse at Children's Memorial Hospital in Chicago as Jacob undergoes a photopheresis treatment which exposes his blood to light and medicine to help the donor cells better adapt to his body. Jacob's donor Marshal Davis, 31, added his name to a bone marrow registry over a decade ago when he was a student at the University of Florida. He got the call to be a donor in 2009 when he was told he was nearly a perfect match with Kowalik. Doctors said abnormalities in Jacob's marrow would eventually develop into acute leukemia without the transplant. less 
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Associated Press | Photo By M. Spencer Green
Sun, May 1, 2011 2:46 PM EDT