Since T-cell receptors have a low affinity for their MHC counterparts, it was historically problematic to label T cells effectively using single MHC-T-cell interactions.
MHC multimers allow for ex vivo selection and proliferation of T-cells specific to viral or tumor-related antigens, which can then be reintroduced to augment the immune system.
[4] Tetramer variants have been developed that, either radiolabelled or coupled to a toxin such as saporin, can be injected into live mice to modulate or even deplete specific T cell populations.
MHC pentamers have been used in the detection of antigen-specific CD8+ T cells in flow cytometry,[12] and are cited in over 750 peer reviewed publications [1], including several in the journals Nature[22] and Science.
[26] While pentamers are licensed for research use only, in 2009 a special dispensation was granted for a team to use them for isolating EBV-specific T cells for mother-daughter transfer, for lifesaving treatment of EBV-associated lymphoma in the daughter.
[27] Pentamers are available for antigens from the following disease areas: adenovirus, HCV, malaria, SIV, autoimmune disease, HIV, transplantation antigens, trypanosoma, cancer, HPV, tuberculosis, chlamydia, HTLV, vaccinia, CMV, influenza, VSV, EBV, LCMV, RSV, West Nile virus, HBV, Listeria, Sendai virus, yellow fever.
Dextramer reagents are fluorescently labeled with FITC, PE or APC, and contain MHC molecules attached to a dextran backbone, which are used to detect antigen-specific T-cells in fluid cells and solid tissue samples using flow cytometry.
This advantage is a result of the increased ability of Dextramers to bind multiple times to a single T-cell, improving the stability of this interaction as compared with other multimer technologies such as pentamers and tetramers.
Further applications include the ability to isolate antigen specific T-cell populations as well as in situ detection using immunohistochemistry (IHC) for various disease states (e.g. solid tumors).