MICROBIAL COLONIZATION INFLUENCES COMPOSITION AND T-CELL RECEPTOR VP REPERTOIRE OF INTRAEPITHELIAL LYMPHOCYTES IN RAT INTESTINE

Studies in mice have shown that the composition of intestinal intraepi thelial lymphocytes (IEL) may be markedly altered by gut microbial col onization. Such modulation was studied in a rat model by the use of ge rm-free and conventionalized animals from which IEL from the small int estine were isolated and analysed by flow cytometry. Conventionalizati on caused expansion as well as phenotypic alterations of T-cell recept or (TCR) alpha/beta(+) IEL in that the proportions of CD4(+) and CD8 a lpha beta(+) TCR alpha/beta(+) cells were increased, while the double negative (CD4(-) CD8(-)) fraction was reduced. Microbial colonization also influenced the TCR V beta repertoire of CD8(+) IEL in that the pr oportions of V beta 8.2(+) and V beta 10(+) cells were increased, wher eas V beta 8.5(+) and V beta 16(+) cells were relatively decreased. Mo reover, conventionalization influenced the levels of TCR cell surface expression in the same V beta subsets. Three-colour flow-cytometric an alysis demonstrated that skewing of the V beta repertoire was most pro nounced in the CD8 alpha alpha(+) subset, although the numerical incre ase of IEL mainly included the CD8 alpha beta(+) subset. In contrast t o IEL, the TCR V beta repertoire in mesenteric lymph nodes was unchang ed after intestinal colonization. These results confirm that TCR alpha /beta(+) IEL subpopulations respond dynamically to the microbial gut f lora and suggest that their V beta repertoire can be shaped by luminal microbial antigens.