Flex-T™ Biotin HLA-A*02:01 SARS-CoV-2 Monomer (RLQSLQTYV)

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280073 25 µg 572€
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CD8+ T cells are essential components of the immune system. They function through TCR recognition of antigens (peptide epitopes) presented by the class I MHC (HLA in humans) molecules.  Thus, TCR recognition of cognate MHC/peptide complex can be utilized for the detection of antigen-specific CD8+ T cells.

The peptide RLQSLQTYV is from SARS-CoV-2 Spike protein (1000-1008).

Product Details
Technical Data Sheet (pdf)

Product Details

Verified Reactivity
PBS containing 0.5% BSA and protease inhibitors
0.1 mg/mL
Storage & Handling
Store frozen at -20°C or -80°C. Aliquot upon receipt before freezing; avoid repeated freeze-thaw cycles. Protect from light.

ELISA - Quality tested
FC - Verified

Recommended Usage

For flow cytometric staining, the suggested use of this reagent is 30 μL of 0.1 mg/mL biotinylated monomer, incubated with desired streptavidin fluorophore conjugate, following our recommended protocol. This will generate tetramers sufficient for 15 tests.

Application Notes

Two-color staining with the same allele/peptide combination is recommended for flow cytometry analysis to increase the resolution and specificity of the assay.

To order custom products please fill out the Custom Flex-T™ Request Form.

Antigen Details

Biology Area
COVID-19, Immunology
Gene ID
3105 View all products for this Gene ID

Related FAQs

Is there any peptide length recommended?

There are no special requirements for the peptides. Peptides that naturally bind to MHC molecules will bind to Flex-T™ reagents. For class I molecules, typical length is about 8 – 10 amino acids. Class II molecules accommodate longer peptides, about 14 – 20 amino acids1.

1) Mohan JF and Unanue ER. Unconventional recognition of peptides by T cells and the implications for autoimmunity. Nat Rev Immunol. 2012 Oct;12(10):721-8.

What are MHC tetramers and what can you do with them?

The T-cell mediated innate immune response is defined by the interaction between antigen presenting cells and T cells, through the Major Histocompatibility Complex (MHC) and the T cell receptor (TCR). MHC molecules present a peptide to antigen-specific T cells that recognize this peptide. Soluble, monomeric MHC molecules bind very weakly to the TCR. However, by making a tetramer through a fluorescently labeled streptavidin conjugate, the complex binds to several TCRs, creating a more stable interaction and making it useful for flow cytometric detection of antigen specific T cells.

How many biotin molecules are per antibody structure?
We don't routinely measure the number of biotins with our antibody products but the number of biotin molecules range from 3-6 molecules per antibody.
I am interested in finding novel peptides instead, are there any resources for this?

There are a number of databases and webpages that can help, these are three of them:


What are the specifications of the UV source?

Long-wave UV, 366 nm, 8 Watts (We recommend, for example, CAMAG cat# 022.9115, or Ultraviolet Crosslinker CL-1000). The distance from the solution to the light source should be 2 – 5 cm (approximately 0.8 – 3 inches).

What is Flex-T™?

Flex-T™ (Flexible-Tetramers) is BioLegend’s brand name for our Soluble MHC product line. It encompasses monomers, the ultraviolet (UV) peptide exchange technology, and all associated products and applications.

Do I need to know the sequence of the UV-labile peptide?

The sequence of the UV-labile peptide is not needed to use the reagent. MHC molecules are not stable without a peptide, so these peptides are used just for two purposes: stabilize the MHC molecules and serve as a place holder to be substituted by the peptide of interest.

Do you offer mouse monomers or tetramers?

Not currently.

Do you offer custom products and services?

Yes, please contact our Custom Solution Team with your request at cst@biolegend.com, or contact your local BioLegend representative.

How do I evaluate the efficiency of the peptide exchange?

Follow the protocol for HLA class I ELISA. An assay positive control is provided (Cat#280301) that can be diluted to a high, medium, and low concentration. Signal intensity can be correlated to affinity of the peptide.

What is the peptide exchange technology and what's the advantage of using it?

Flex-T™ MHC monomers are loaded with a peptide that can be degraded by the use of a UV light source. This allows for a peptide exchange when the UV irradiation is done in the presence of the peptide of interest (which is not UV-labile). This flexibility permits the screening of virtually any peptide of interest with enough affinity for the MHC allele that it is loaded onto.

Is it feasible to screen not just peptides, but also several specificities of antigen-specific T cells in one sample?

With the traditional pre-assembled Tetramer approach, this is difficult to do, and not cost-effective. With Flex-T™ technology, as there is more flexibility to assemble the tetramers, it is easy and affordable to screen a sample for several specificities2. To facilitate this approach, a combinatorial color coding system has been developed. Please visit the Flex-T™ webpage for a detailed description.

2) Hadrup SR et al. Parallel detection of antigen-specific T-cell responses by multidimensional encoding of MHC multimers. Nat Methods. 2009 Jul;6(7):520-6.

Is there any advantage in buying biotinylated monomers?

Yes, the same monomer can be assembled with different Streptavidin conjugates, providing great flexibility for color choices. Additionally, it can be stored frozen and the tetramer assembled shortly before the experiment. This increases the storage time of the reagent.

Go To Top Version: 1    Revision Date: 11.11.2020

For Research Use Only. Not for diagnostic or therapeutic use.


This product is supplied subject to the terms and conditions, including the limited license, located at www.biolegend.com/terms) ("Terms") and may be used only as provided in the Terms. Without limiting the foregoing, BioLegend products may not be used for any Commercial Purpose as defined in the Terms, resold in any form, used in manufacturing, or reverse engineered, sequenced, or otherwise studied or used to learn its design or composition without express written approval of BioLegend. Regardless of the information given in this document, user is solely responsible for determining any license requirements necessary for user’s intended use and assumes all risk and liability arising from use of the product. BioLegend is not responsible for patent infringement or any other risks or liabilities whatsoever resulting from the use of its products.


BioLegend, the BioLegend logo, and all other trademarks are property of BioLegend, Inc. or their respective owners, and all rights are reserved.


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