Naïve T cells are continually generated in the thymus, where each cell undergoes DNA rearrangement to generate a unique T-cell receptor and where each cell is screened against autoreactivity and
for an affinity (“restriction”) for self-MHC.
Each naïve T cell recirculates from blood through a lymph node and back to blood every 12 to 24 hours.
If a naïve T cell does encounter an antigen-presenting cell [in the lymph node] that expresses an MHC/peptide to which it can bind, it will initiate an activation program.
(Source: International Review of Cell and Molecular Biology, 2016)
