Background Immunotherapy has revolutionized the treatment of cancer, and has been instated as a ‘pillar’ of modern cancer treatments alongside chemotherapy, radiotherapy and surgery. Most tumor immunotherapy developments to date have focused on cytotoxic CD8⁺ T cells. Increasingly, γδ T cells are being considered as the next-generation tumor immunotherapy against difficult to treat solid tumors due to their potent cytotoxic and cytolytic functions, and natural tropism for the tumor microenvironment. Moreover, γδ T cells can recognize a broad range of tumors and infected cells without the requirement of antigen presentation via major histocompatibility complex (MHC) molecules. Previous studies have shown that a high number of γδ T cells within tumors is strongly correlated with overall patient survival across 25 cancer types.

Methods We have isolated and expanded human Vδ1⁺ and Vδ2⁺ T cells and performed in vitro T cell killing assay. In vitro isolated human Vδ2⁺ T cells were used for adoptive cell transfer in tumor-bearing NSG mice.

Results In our hands, we show that human Vδ1⁺ and Vδ2⁺ T cell constitute only 0.05 to 0.62% and 0.34 to 3.02%, respectively of total circulating T cells. We are now routinely isolating and expanding human Vδ1⁺ and Vδ2⁺ T cells and have immunophenotyped and validated their capability to kill different types of tumor cells in vitro. Additionally, we show that in vitro isolated human Vδ2⁺ T cells can slow tumor growth in vivo and prolong the survival of tumor-bearing NSG mice when adoptively transferred.

Conclusions Collectively, our data showed that human γδ T cells are promising targets for tumor immunotherapy development.

Ethics Approval ‘This study was approved by Australian Red Cross for the isolation of human Vδ2⁺ γδ T cells from healthy donors’ peripheral blood mononuclear cells, agreement number: 21-07VIC-09.’

‘This study was approved by Austin Health Animal Ethics Committee for adoptive cell transfer of human Vδ2⁺ γδ T cells into NSG mice, AEC Reference number: A2020/05661.’