Slow transit facilitates the detection of rare self-antigens. The self-pMHC ligands required for survival by a given clone are assumed to be distributed at random across all LNs. (A) Cumulative probability of a single cell encountering a self-antigen present a frequency of 1 in 10⁵, for different transit times. (B) The probability of detection by 180 days as function of self-antigen density. In both panels predictions quickly saturate for transit times longer than 12 hours (not shown).