Major histocompatibility complex (MHC) class I and class II molecules share the task of presenting peptides on the cell surface for recognition by T cells and play a pivotal role in the adaptive immune system.

Peptide-MHC (pMHC) complexes are recognized by CD4+ and CD8+ T cells expressing a repertoire of hypervariable αβ T cell receptors (TCRs). The interaction between the pMHC complex and a cognate TCR is short lived and of low affinity. By the multimerization of four pMHC molecules on a streptavidin scaffold, the tetramer binds to TCR with high affinity and specificity. Thus, pMHC tetramers can be used to identify, monitor, and handle T cells through direct and specific staining.

The pMHC molecules including HLA-A, HLA-B, HLA-C and HLA-DR are biotinylated. Available formulations are MHC monomers and tetramers.

• More than 30 MHC class I allotypes are available to be made into tetramers with optional labels.
• The tetramers with phycoerythrin (PE) and allophycocyanin (APC) fluorochromes are available for flow cytometric analysis to characterize and quantify epitope-specific T cells.