TdT expression levels and junction characteristics of productive Ig and TR rearrangements. (A) Expression of TdT is higher during the early Ig rearrangements and TR rearrangements, measured at RNA level by microarray (gene expression)^35,36  and at the protein level by flow cytometry. (B) Median number of N-nucleotides, (C) deletions, and (D) P-nucleotides in productive unique IgH, IgK, IgL, TRD, and TRB rearrangements in healthy controls and XRCC4/LIG4- and XLF-deficient patients. The numbers of productive unique rearrangements used to calculate the median are listed in supplemental Table 1. *P ≤ .05; **P ≤ .01; ***P ≤ .001 by 2-tailed Mann-Whitney U test.