Human MR1 Tetramers

The MHC Class-1 related molecules, MR1, are non-polymorphic proteins that serve key functions in the immune response. They present bacterial metabolites derived from antigens to  mucosal-associated invariant T (MAIT) cells and present self-antigens to MR1-restricted T cells.1

MAIT cells in the Immune Response

Mucosa-associated invariant T (MAIT) cells are strikingly abundant and conserved cells that are involved in many critical immunological functions.  They express the semi-invariant αβ TCRs. These are involved in the recognition of biosynthetic derivatives of riboflavin (vitamin B12) synthesis, which is a widely studied function of MR-1 and MAIT cells. 2

The TCRs exhibited by conventional T-cells are highly variable. These, thus, have the capability to specifically target a variety of peptide epitopes. This, however, involves limited frequency of an individual perptide-specific T-cell at first encounter with an antigen. MAIT cells are abundant and invariant. Each TCR recognizes the same ligand. Thus, in the early immune response, MAIT cells exceed the number of antigen-specific conventional T-cells.2

Common ligands for MR1

Common ligands for MR1 include reduced 6-hydroxymethyl-*-D-ribityllumazine, 5-(2-oxopropylideneamino)-6-D-ribiylaminoyracil and 6-formylpterin. The features and structure of these have been given in the table below:

Ligand Table

The MBLI MR1 Tetramer

MBLI offers MR1 tetramers for your research needs. These are prepared by tetramerization of biotinylated human MR1/β2m complexes using phycobiliprotein-labelled streptavidin

Product Highlights

Product CodeProduct NameSize
TS-HMRV2-1T-Select Human MR1 Tetramer v2-PE50 tests
TS-HMRV2-2T-Select Human MR1 Tetramer v2-APC50 tests

Preparing the ligand-loaded MR1 Tetramer

*These tetramers do NOT include the MR1 ligand


  • 5-A-RU STOCK solution: 5-A-RU (Toronto Research Chemicals, Code No. A629245) 2.76 mg/mL (in ddw)
  • Methylglyoxal solution: Mix 1 µL of methylglyoxal (Sigma, M0252-25ML) and 406 µL of water.
  • Add 0.72 µL of 5-OP-RU to MR1 Tetramer (100 µL).

Ac-6-FP [A ligand for negative control of MR1 tetramer]

Ac-6-FP (Carbosynth, Code No. FA16935) 2 mg/mL (in 10 mM NaOH)
Add 1 µL of Ac-6-FP to 10 µL of MR1 Tetramer

Example 1: Cell staining using PE-labeled MR1 Tetramers

PBMCs from healthy donors were collected from freshly isolated heparinized peripheral blood according to standard methods. These PBMCs were stained with T-Select Human MR1 Tetramer v2-PE loaded with 5-OP-RU or Ac-6-FP, as described in the datasheet.
The single lymphocyte population was defined using the FSC/SSC and FSC-H/FSC-A gates, and the viable cell population was defined using the FSC/7-AAD gate.





*Numbers in the upper right quandrants represent the percentages of  T-Select Human MR1 Tetramer+ cells relative to the total CD3+cells.

Example 2: Staining comparison of MR1 Tetramer products

PBMCs from healthy donors were stained with T-Select Human MR1 Tetramer v2-APC loaded with 5-OP-RU or Ac-6-FP, or unloaded. It was compared with staining data using human MR1 tetramer of competitor A loaded with 5-OP-RU or 6-FP, or unloaded.
The single lymphocyte population was defined using the FSC/SSC and FSC-H/FSC-A gates, and the viable cell population was defined using the FSC/7-AAD gate.



  1. Alessandro V, et al. Front. Immunol. 11: 751 (2020)
  2. Timothy SCH and Xie-Wei Z Front. Immunol. 11: 1014 (2020)
  3. Hamish EGM and Jose AV Trends in Immunology 38(9): 679-689 (2017)
  4. Dusseaux M, et al. Blood 117:1250-1259 (2011)
  5. Kjer-nielsen L, et al. Nature 491:717-723 (2012)
  6. Reantragoon R, et al. J Exp Med 210:2305-2320 (2013)
  7. Corbett AJ, et al. Nature 509:361-365 (2014)
  8. Eckle SB, et al. J Exp Med 211:1585-1600 (2014)
  9. Howson LJ, et al. Front Immunol 6:303 (2015)
  10. Mondot S, et al. Immunogenetics 68:537-548 (2016)
  11. Keller AN, et al. Nat Immunol 18:402-411 (2017)
  12. Keller AN, et al. Curr Opin Immunol 46:66-74 (2017)
  13. Greene JM, et al. Mucosal Immunol 10:802-813 (2017)
  14. Kjer-nielsen L, et al. Immunol Cell Biol 6:573-587 (2018)
  15. Chiba A, et al. Front Immunol 9:1333 (2018)

Learn more about the other types of MHC Molecules