Human cytomegalovirus expands a CD8

CD8(+) T cells are critical mediators of adaptive immunity but may also exhibit innate-like properties such as surface expression of NKG2C, an activating receptor typically associated with natural killer (NK) cells. We demonstrate that, similar to NK cells, NKG2C(+)TCRαβ(+)CD8(+) T cells are associated with prior human cytomegalovirus (HCMV) exposure. In addition to expressing several NK cell markers such as CD56 and KIR, NKG2C(+)CD8(+) T cells are oligoclonal and do not upregulate PD-1 even in response to persistent activation. Furthermore, we found that NKG2C(+)CD8(+) T cells from some individuals exhibited strong effector function against leukemia cells and HCMV-infected fibroblasts, which was dictated by both NKG2C and TCR specificity. Transcriptomic analysis revealed that the transcription factor BCL11B, a regulator of T cell developmental fate, is significantly downregulated in NKG2C(+)CD8(+) T cells when compared to conventional NKG2C(−)CD8(+) T cells. BCL11B deletion in conventional CD8(+) T cells resulted in the emergence of a similar innate-like CD56(+)CD94(+)DAP12(+)NKG2C(+)CD45RA(+)CCR7(−)PD-1(−/low) T cell population with activity against HLA-E(+) targets. Based on their intrinsic capacity to recognize diseased cells coupled with lack of PD-1 induction, NKG2C(+)CD8(+) T cells represent a lymphocyte population that resides at the boundary between innate and adaptive immunity, presenting an attractive alternative for cellular therapy, including CAR T-based therapies.