Class I and Class II MHC
Monomers & Tetramers

Mammalian-Expressed Catalog & Custom Peptide-MHC Complexes

Class I and Class II Alleles

Product Features

Choice of Allele

Biotinylation & Fluorescent Labels

Verified Bioactivity

Catalog Products In Stock

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Shop by Allele

Class I Alleles - Human

Class I Alleles - Mouse

Class II Alleles or Other Alleles

For other class I alleles, non-classical alleles, or class II alleles, submit our Custom MHC Request Form.

Shop by Peptide Sequence

Custom Peptide

For MHCs with custom peptide sequences, submit our Custom MHC Request Form.

Alternatively, try a Peptide-Ready MHC to load your peptide in-house onto an MHC tetramer or monomer.

Product Validation Data

Human NY-ESO-1 (HLA-A*02:01) Tetramer

Anti-NY-ESO-1 (HLA-A*02:01) Antibody, hFc Tag captured on CM5 Chip via Protein A can bind Human NY-ESO-1 (HLA-A*02:01) Tetramer, His Tag with an affinity constant of 0.09 nM as determined in SPR assay (Biacore T200).

Human KRAS G12V (HLA-A*03:01)

Human KRAS G12V (HLA-A*03:01) , His Tag captured on CM5 Chip via anti-his antibody can bind Anti-KRAS G12V (HLA-A*03:01) Antibody with an affinity constant of 0.11 μM as determined in SPR assay (Biacore T200).

Biotinylated Human P53 R175H (HLA-A*02:01)

Immobilized Anti-P53 R175H (HLA-A*02:01) Antibody, hFc Tag at 5μg/mL (100μL/well) on the plate. Dose response curve for Biotinylated Human P53 R175H (HLA-A*02:01) , His Tag with the EC50 of 1.6μg/mL determined by ELISA.

Human NY-ESO-1 (HLA-A*02:01) Tetramer

As verified by ELISA, the activity of NY-ESO-1 (HLA-A*02:01) tetramer expressed in mammalian cells and E. coli is comparable, providing you with more choices for research.

Browse All MHC Products

Select a column header to sort by type, species, allele, neoantigen, or peptide.

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Peptide-Ready MHC: Load your own peptide

Load your own MHC monomer or tetramer in-house with our peptide-free MHCs.

→ Quick & simple peptide loading procedure

→ Monomer / Tetramer

→ Fluorescent Labeling

→ Class I and Class II Alleles

→ Biotinylation

MHC Product Types


Our MHC peptide monomers are mammalian-expressed to ensure the natural configuration and have a His-Avi tag at the C-terminus. The Avi tag is a 15-amino acid sequence, which has a high affinity for biotin and can be specifically biotinylated by BirA.


MHC tetramers are complexes of four peptide-MHC biotinylated monomers bound to streptavidin molecules. The enhanced avidity of MHC tetramers and TCR interactions can have a significant impact for detecting antigen-specific T cells. They allow for direct detection, phenotyping, and enumeration of antigen-specific T cells within a polyclonal T cell population. KACTUS offers class I and class II tetramers.

Fluorescent Tetramer

Fluorescent MHC tetramers can be used to identify T cells that recognize a particular peptide-MHC complex. By labeling T cells with MHC tetramers, the frequency and distribution of antigen-specific T cells can be determined and sorted by FACS in a cell population. MHC tetramers can also be used to monitor immune responses to vaccines, infections and diseases by measuring the frequency of antigen-specific T cells over time to track the efficacy of a treatment.

MHC-I Virus-Like Particles

In combination with our Virus-Like Particles (VLP) technology platform, we have introduced multivalent fluorescent MHC I.  These MHC I-VLP complexes are about 750 Å in diameter, compared to the MHC I monomer size of 70 Å. Each VLP contains approximately 250 copies of MHC I, resulting in boosted fluorescence quantum yield for enhanced detection of TCR binding. We currently offer FITC- and APC-equivalent options for MHC I-VLP fluorescence labeling.

Peptide-Ready MHC

Neoantigens offer a distinct advantage in their unique tumor-specific and normal tissue-absent feature, presenting ideal targets for effective and personalized tumor-specific immunotherapy. We have developed Peptide-Ready MHCs (prMHC), which are composed only of the α heavy chain and β2-microglobulin (β2m) light chain for loading your own neoantigen.

Learn more about Peptide-Ready MHCs here.

Chimeric MHC

Chimeric MHCs have the human α3 immunoglobulin-like domain replaced with the mouse α3 domain. This modification enhances antigen specificity for antibody discovery. These mammalian-expressed Chimeric MHCs retain their normal conformation to increase the likelihood of generating peptide-specific antibodies while decreasing the frequency of non-specific antibodies and making screening less labor-intensive.

Custom MHC Complexes

Choice of mammalian or E. coli expression systems

Monomers, Tetramers, Biotinylation, Fluorescent Labels

Multi-faceted biological activity verification (ELISA, SPR, FACS, etc.)

Choice of Class I or Class II Alleles

Choice of PE, APC, or other fluorescent label

Various species: Human, mouse, monkey, etc.

Soluble TCR Expression & SPR Analysis

→ Production of various formats of soluble TCRs, including scFv-TCR, TCR-His, etc. 

→ TCR engineering to optimize soluble TCR expression based on TCR modeling

→ SPR analysis of soluble TCR & Peptide-Ready MHC/Peptide-MHC interactions


→ HLA-G Monomers and Tetramers


→ APOE Proteins

→ Custom HLA-G & LILR Proteins

Major Histocompatibility Complex

The MHC (Major Histocompatibility Complex) is a major histocompatibility complex, which is a highly polymorphic family of cell surface proteins, also known as HLA in humans. MHC can bind to peptide fragments of intracellular antigens to form MHC-peptide complexes, which are then transported to the cell surface and recognized by the corresponding T cell receptor (TCR) to initiate an immune response.

In humans, the main types of MHC involved in antigen presentation are MHC I and MHC II. MHC I, after binding antigen peptides, is recognized by CD8+ T cells, while MHC II, after binding peptides, is recognized by CD4+ T cells. MHC-peptide complexes represent a category of intracellular antigen targets. Their unique binding pattern with TCR plays a crucial role not only in adaptive immune processes but also holds significance for TCR-related therapies such as TCR-T development.

Mechanism of MHC involvement in antigen presentation (Anthony W. Purcell, et al., 2019)

MHC Class I (MHC-I)

MHC-I molecules play a crucial role in the immune system by presenting peptide antigens to cytotoxic T cells. These heterotrimers consist of a transmembrane MHC heavy chain, a light chain known as β2-microglobulin (β2m), and an 8-10 peptide antigen. The heavy chain contains two peptide binding domains (α1 and α2), an immunoglobulin-like domain (α3), and a transmembrane region. The folding of the α1 and α2 domains forms a groove where peptide antigens bind to the MHC-I molecule. β2m stabilizes the peptide binding groove and MHC I presentation.

A single nucleated cell expresses 5x10⁵ copies of each MHC I molecule, presenting a variety of peptides simultaneously on the cell surface to CTLs. Accumulating genomic mutations in cancers result in the production of tumor-specific antigens or neoantigens, which can be presented by MHC I molecules of tumor cells to CTLs.

MHC Class 1 complex (MHC-I) containing an α-chain spanning the cell membrane and an extracellular β2m (β2-microglobulin) connected to this chain.

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1. Kurosawa et al., Development of a T‐cell receptor mimic antibody targeting a novel Wilms tumor 1‐derived peptide and analysis of its specificity. Cancer Sci. 2020 Oct; 111(10): 3516–3526.

2. Doubrovina et al., Mapping of novel peptides of WT-1 and presenting HLA alleles that induce epitope-specific HLA-restricted T cells with cytotoxic activity against WT-1(+) leukemias. Blood. 2012 Aug 23;120(8):1633-46