AAT levels. Serum levels of AAT were measured in patients with SR-aGVHD at enrollment before administration of ATT and in paired samples obtained at 2, 4, and 8 weeks after the start of AAT treatment. AAT administration was completed after 4 weeks. Median values are depicted. Error bars represent standard deviations. *P = .01; **P < .01. N, number of paired samples at a given time point.