The peripheral CD8 T cell repertoire is largely independent of the presence of intestinal flora

While numerous studies have analyzed the shaping of T cell repertoires by s elf or foreign peptides, little is known on the influence of commensal self peptides derived from the intestinal flora (IF), Here, we have analyzed na ive and immune repertoires in mice devoid of IF [germ-free (GF) mice]. Firs t, by means of an extensive CDR3 beta sequencing strategy, we show that the naive peripheral CD8 T cell repertoire does not exhibit a major imprint of IF antigens. Second, using MHC-peptide tetramers, CDR3 beta length distrib ution analyses and TCR sequencing, we show that cytotoxic T lymphocyte (CTL ) responses specific for two distinct epitopes are quasi-identical in norma l and GF mice. Our findings indicate that, in general, peptides derived fro m the intestinal microflora have little if any influence on CTL responses i n the mouse.