  The diversity of T-cell receptor (TCR) repertoires is achieved by a
combination of two intrinsically stochastic steps: random receptor generation
by VDJ recombination, and selection based on the recognition of random
self-peptides presented on the major histocompatibility complex. These
processes lead to a large receptor variability within and between individuals.
However, the characterization of the variability is hampered by the limited
size of the sampled repertoires. We introduce a new software tool SONIA to
facilitate inference of individual-specific computational models for the
generation and selection of the TCR beta chain (TRB) from sequenced repertoires
of 651 individuals, separating and quantifying the variability of the two
processes of generation and selection in the population. We find not only that
most of the variability is driven by the VDJ generation process, but there is a
large degree of consistency between individuals with the inter-individual
variance of repertoires being about 2% of the intra-individual variance. Known
viral-specific TCRs follow the same generation and selection statistics as all
TCRs.
