title: Microbial colonization induces oligoclonal expansions of intraepithelial CD8 T cells in the gut.
abstract: Two populations of CD8(+) IEL generally express restricted, but apparently random and non-overlapping TCR repertoires. Previous studies in mice suggested that this could be explained by a dual origin of CD8(+) IEL, i.e. that CD8alphabeta(+) IEL derive from a few peripheral CD8(+) T cell lymphoblasts stimulated by microbial antigens in gut-associated lymphoid tissue, whereas CD8alphaalpha(+) IEL descend from an inefficient intestinal maturation pathway. We show here that the gut mucosa, instead, becomes seeded with surprisingly broad and generally non-overlapping CD8 IEL repertoires and that oligoclonality is induced locally after microbial colonization. In germ-free (GF) rats, both CD8alphabeta(+) and CD8alphaalpha(+) IEL displayed surprisingly diverse TCR Vbeta repertoires, although beta-chain diversity tended to be somewhat restricted in the CD8alphaalpha(+) subset. CDR3 length displays in individual Vbeta-Cbeta and Vbeta-Jbeta combinations generally revealed polyclonal distributions over 6-11 different lengths, similar to CD8(+) lymph node T cells, and CDR3beta sequencing provided further documentation of repertoire diversity. By contrast, in ex-GF rats colonized with normal commensal microflora, both CD8alphabeta(+) and CD8alphaalpha(+) IEL displayed oligoclonal CDR3 length distributions for most of the Vbeta genes analyzed. Our data suggest that microbial colonization induces apparently random clonal expansions of CD8alphabeta(+) and CD8alphaalpha(+) IEL locally in the gut.
authors.affiliation: LIIPAT, Institute of Pathology, Rikshospitalet University Hospital, Oslo, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Helgeland
authors.forename: Erik
authors.initials: E
authors.lastname: Dissen
authors.forename: Ke-Zheng
authors.initials: KZ
authors.lastname: Dai
authors.forename: Tore
authors.initials: T
authors.lastname: Midtvedt
authors.forename: Per
authors.initials: P
authors.lastname: Brandtzaeg
authors.forename: John Torgils
authors.initials: JT
authors.lastname: Vaage
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002455:Cell Division / Q000276:immunology; D007413:Intestinal Mucosa / Q000166:cytology / Q000276:immunology* / Q000382:microbiology; D007421:Intestine, Small / Q000166:cytology / Q000276:immunology* / Q000382:microbiology; D051381:Rats; D011948:Receptors, Antigen, T-Cell / Q000276:immunology
chemical_list: D011948:Receptors, Antigen, T-Cell