Mucosal-associated invariant T (MAIT) cells: an evolutionarily conserved T cell subset

• Published in: Microbes and infection 2005-03, Vol.7 (3), p.552-559
• Main Authors: Treiner, Emmanuel, Duban, Livine, Moura, Ivan Cruz, Hansen, Ted, Gilfillan, Susan, Lantz, Olivier
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biological Evolution; Commensal flora; Fundamental and applied biological sciences. Psychology; Gene Expression; Humans; Immunity, Mucosal; Intestinal Mucosa - immunology; Killer Cells, Natural - immunology; Lamina propria; Life Sciences; Microbiology; MR1; Mucosal immune system; T cell; T cell selection; T-Lymphocyte Subsets - immunology; TCRα chain
• ISSN: 1286-4579; 1769-714X
• DOI: 10.1016/j.micinf.2004.12.013

Besides mainstream TCRαβ 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 Vα14 TCRα 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 hVα7.2/mVα19-Jα33 TCRα chain paired with a restricted set of Vβ 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.