The diversity of the T cell repertoire of mature T splenocytes is generated
, in the thymus, by pairing of alpha and beta variable domains of the cup T
CR and by the rearrangements of various gene segments encoding these domain
s. In the periphery, it results from competition between various T cell sub
populations including recent thymic migrants and long-lived T cells, Quanti
tative data on the actual size of the T cell repertoire are lacking. Using
PCR methods and extensive sequencing, we have measured for the first time t
he size of the TCR-alpha beta repertoire of naive mouse T splenocytes, Ther
e are 5-8 x 10(5) different nucleotide sequences of BV chains in the whole
spleen of young adult mice. We have also determined the size of the alpha b
eta repertoire in a subpopulation of AV2(+) T splenocytes, which allows us
to provide a minimum estimate of the cup repertoire. We find that the mouse
spleen harbors about 2 x 10(6) clones of about 10 cells each. This figure,
although orders of magnitude smaller than the maximum theoretical diversit
y (estimated up to 10(15)), is still large enough to maintain a high functi
onal diversity.