Rihanna, 50 Cent, and Gossip Girl star Leighton Meester have combined their star power in order to help find a donor for an upper West Side infant in need of a bone marrow transplant. Each celebrity had their cheeks swabbed in order to see if they could donate marrow to 1-year-old Ayelet Galena. The ill baby suffers from dyskeratosis congenital, a rare life-threatening disease.

Each star is hoping their respective fan bases will get tested in order to help Ayelet find a donor. Katharina Harf, the COO of DKMS, a German bone-marrow donor center, told the New York Daily News, "It started out with Rihanna tweeting, and then I asked 50 Cent, he has helped us before. And then [Ayelet's] dad got all these other artists and bands aboard." Since then Pharrell and Linkin Park have also gotten involved.

(Photos from left: Pascal Le Segretain/Getty Images, Isaac Brekken/Getty Images, Andy Kropa/Getty Images)