A, Mean (SEM) production of reactive oxygen species (ROS) in fibroblasts exposed to 25°C for 5 days simulating cold with a rewarming phase at 37°C for 24 hours or without a rewarming phase at 37°C for 48 hours. B, Mean (SD) increased senescence as shown by staining for β-galactosidase activity after cold exposure for 5 days followed by 24 hours of rewarming. C, Mean (SEM) messenger RNA expression of IFI27 after exposure to cold (wild-type [WT], n = 3; familial chilblain lupus [FCL], n = 2; Aicardi-Goutières-Syndrome [AGS], n = 2). Mann-Whitney test or unpaired t test.