Fig. 3

10¹¹ human TCRs have to recognize 10²⁰ peptides: a TCR repertoire (purple sphere) is several magnitudes less diverse than the total set of peptides that are presented by MHC molecules (pMHC) (orange sphere). Hence, a necessary feature of a TCR repertoire is that a T-cell is able to recognize and respond to many peptides, but one TCR only recognizes and responds to peptides closely related to the original agonist peptide (similar colors representing peptide relatedness). Modified from Mandl and Germain 2014 [73]