Linear regression analysis of TL measurements. Relative TL (T/S ratio), an estimated concentration of the telomere DNA (T) repeats divided by the single-copy (S) hemoglobin gene in participant 401, forced through baseline time point (ranging from baseline to 80 months after GT) (A); participant 402 forced through baseline time point (ranging from baseline to 120 months after GT) (B); participant 403 (ranging from 5 to 118 months after GT) (C); participant 404 forced through baseline time point (ranging from baseline to 96 months after GT) (D); participant 405 intercept forced through baseline time point (ranging from baseline to 96 months after GT) (E); participant 406 (ranging from 6 to 72 months after GT) (F); participant 407 (ranging from 10 to 96 months after GT) (G); participant 408 forced through baseline time point (ranging from 1 to 84 months after GT) (H); participant 409 (ranging from baseline to 84 months after GT) (I); participant 410 (ranging from 6 to 54 months after GT) (J); and unpaired t test of TLs in 16 controls and all time points (ranging from baseline to 120 months after GT) in patients with ADA-SCID (K). Dotted lines represent 95% confidence bands of the best-fit line (only for those patients without a forced baseline intercept). P-values calculated to represent significant slope deviation from 0.