Mucosal-associated invariant T (MAIT) cells: an evolutionarily conserved T cell subset.
Besides mainstream TCRalphabeta T cells harboring a very diverse repertoire, two subsets display an evolutionarily conserved invariant repertoire. This striking conservation indicates important and unique functions. CD1d-restricted NK-T cells expressing an invariant Valpha14 TCRalpha chain have been implicated in microbial and tumor responses as well as in auto-immunity. In this review, we describe the other subset, which bears the canonical hValpha7.2/mValpha19-Jalpha33 TCRalpha chain paired with a restricted set of Vbeta segments. These invariant T cells are present in mice, humans and cattle. They are preferentially located in the gut lamina propria (LP) of humans and mice and are therefore called mucosal-associated invariant T (MAIT) cells. Selection/expansion of this population requires B lymphocytes expressing MR1, a monomorphic major histocompatibility complex class I-related molecule that is also strikingly conserved in diverse mammalian species. MAIT cells are not present in germ-free mice, indicating that commensal flora is required for their expansion in the gut LP. The nature of the ligand and the putative functions of these MAIT cells are discussed.
Treiner
Emmanuel
E
Laboratoire d'Immunologie and Inserm U520, Institut Curie, 26, rue d'Ulm, 70005 Paris, France.
Duban
Livine
L
Moura
Ivan Cruz
IC
Hansen
Ted
T
Gilfillan
Susan
S
Lantz
Olivier
O
D000818:Animals; D005075:Biological Evolution; D015870:Gene Expression; D006801:Humans; D018928:Immunity, Mucosal; D007413:Intestinal Mucosa / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology; D016176:T-Lymphocyte Subsets / Q000276:immunology*