Research ArticleIMMUNODEFICIENCY

Absence of mucosal-associated invariant T cells in a person with a homozygous point mutation in MR1

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Science Immunology  24 Jul 2020:
Vol. 5, Issue 49, eabc9492
DOI: 10.1126/sciimmunol.abc9492

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A human immune system sans MAITs

Here, Howson et al. set out to determine the genetic basis of immunodeficiency in a patient with persistent tattoo-associated human papilloma virus–positive warts. Whole-exome sequencing led them to identify a rare point mutation Arg31His (R9H in the mature protein) in both copies of the MR1 gene. MR1 encodes an MHC-like molecule that presents bacteria-derived riboflavin metabolites to mucosal-associated invariant T (MAIT) cells. MAIT cells represent ~5% of circulating human T cells. MAIT cells reside in high frequency in mucosal tissues and provide enhanced immunity against bacterial and viral infections. By solving the structure of the MR1-R9H mutant, they demonstrate that this mutation disrupted the ligand-binding domain of MR1. Consistent with this finding, the individual lacked circulating MAIT cells.

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