Kelly Sullivan, a molecular biologist at the Linda Crnic Institute for Down Syndrome at the University of Colorado, Anschutz Medical Campus who was not involved in the work, agrees that the data showing USP18 in the blood cells aren’t the most compelling, but notes that low levels of a protein don’t preclude it from having a large effect. He says that the data comparing DS and healthy blood cells do validate the authors’ claim that the DS cells are partially desensitized.