Abstract
Human phosphoantigen-reactive Vγ9Vδ2 T cells possess several characteristics, including MHC-independent recognition of tumor cells and potent killing potential, that make them attractive candidates for cancer immunotherapeutic approaches. Injectable preparations from the hemi-parasite plant Viscum album L. (European mistletoe) are commonly prescribed as complementary cancer therapy in European countries such as Germany, but their mechanism of action remains poorly understood. Here, we investigated in-depth the in vitro response of human T cells towards mistletoe-extract drugs by analyzing their functional and T-cell-receptor (TCR) response using flow cytometry and high-throughput sequencing respectively. Non-fermented mistletoe-extract drugs (AbnobaViscum), but not their fermented counterparts (Iscador), induced specific expansion of Vγ9Vδ2 T cells among T cells. Furthermore, AbnobaViscum rapidly induced the release of cytotoxic granules and the production of the cytokines IFNγ and TNFα in Vγ9Vδ2 T cells. This stimulation of anti-cancer Vγ9Vδ2 T cells was mediated by the butyrophilin BTN3A, did not depend on the accumulation of endogenous phosphoantigens and involved the same Vγ9Vδ2 TCR repertoire as those of phosphoantigen-reactive Vγ9Vδ2 T cells. These insights highlight Vγ9Vδ2 T cells as a potential target for mistletoe-extract drugs and their role in cancer patients receiving these herbal drugs needs to be investigated.
Highlights
T cell-based cancer immunotherapy has become a main therapy arm in the clinic besides surgery, radio- and chemotherapy
We obtained four commercially available Viscum album L. (VA) extracts from two companies that derive them from the same host trees but use different preparatory methods: non-fermented extracts are AbnobaViscum Pini (AP) and AbnobaViscum Mali (AM) and fermented products are Iscador Malus (IM) and Iscador Pinus (IP)
As heat-treatment is not performed on the mistletoe-extracts that are injected in cancer patients, we preferred to test an alternative method to prevent the cytotoxic effects in order to verify whether the heat-treatment was essential for possible effects on Vγ9Vδ2 T cells [26]
Summary
T cell-based cancer immunotherapy has become a main therapy arm in the clinic besides surgery, radio- and chemotherapy. The γδ TCR is generated by the somatic recombination of the TRG and TRD loci, combining different variable (V), diversity (D, only in TRD), and joining (J) gene segments [3,4]. This combinational diversity together with junctional diversity can result in a large variation in possible V(D)J junctions, called complementary-determining-region-3 (CDR3), the part of the
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
