TCRβrearrangements without D-segment are common, abundant and public

T cells play an important role in adaptive immunity. An enormous clonal diversity of T-cells with a different specificity, encoded by the T-cell receptor (TCR), protect the body against infection. Most TCR β chains are generated from a V-, D-, and J-segment during recombination in the thymus. Although complete absence of the D-segment is not easily detectable from sequencing data, we find convincing evidence for a substantial proportion of TCR β rearrangements lacking a D-segment. Additionally, sequences without a D-segment are more likely to be abundant within individuals and/or shared between individuals. We find that such sequences are preferentially generated during fetal development and persist within the elderly. Summarizing, TCR β rearrangements without a D-segment are not uncommon, and tend to allow for TCR β chains with a high abundance in the naive repertoire.