NKG2A is a late immune checkpoint on CD8 T cells and marks repeated stimulation and cell division

Abstract

The surface inhibitory receptor NKG2A forms heterodimers with the invariant CD94 chain and is expressed on a subset of activated CD8 T cells. As antibodies to block NKG2A are currently tested in several efficacy trials for different tumor indications, it is important to characterize the NKG2A+ CD8 T cell population in the context of other inhibitory receptors. Here we used a well‐controlled culture system to study the kinetics of inhibitory receptor expression. Naïve mouse CD8 T cells were synchronously and repeatedly activated by artificial antigen presenting cells in the presence of the homeostatic cytokine IL‐7. The results revealed NKG2A as a late inhibitory receptor, expressed after repeated cognate antigen stimulations. In contrast, the expression of PD‐1, TIGIT and LAG‐3 was rapidly induced, hours after first contact and subsequently down regulated during each resting phase. This late, but stable expression kinetics of NKG2A was most similar to that of TIM‐3 and CD39. Importantly, single‐cell transcriptomics of human tumor‐infiltrating lymphocytes (TILs) showed indeed that these receptors were often coexpressed by the same CD8 T cell cluster. Furthermore, NKG2A expression was associated with cell division and was promoted by TGF‐β in vitro, although TGF‐β signaling was not necessary in a mouse tumor model in vivo. In summary, our data show that PD‐1 reflects recent TCR triggering, but that NKG2A is induced after repeated antigen stimulations and represents a late inhibitory receptor. Together with TIM‐3 and CD39, NKG2A might thus mark actively dividing tumor‐specific TILs.

Sculpting the tumour microenvironment by combining radiotherapy and ATR inhibition for curative-intent anti-PD-L1- and anti-NKG2A-based adjuvant immunotherapy

“…Dual anti-NKG2A/-PD-L1 immunotherapy, added as an adjuvant to ATRi/RT, drives significant infiltration of PD-1 high /proliferative/effector memory cytotoxic CD8 and CD4 conv T cells in tumours. We found that addition of anti-NKG2A antibody to the combination was essential to shifting the cell cycle towards the G2/M phase in T cells, which was in line with previous data showing repeated cell division in NKG2A + CD8 T cells 33 . These results are also consistent with findings of elevated proliferative capacity of CD8 T cells in response to combined RT and dual NKG2A/PD-1 blockade 34 .…”

“…Enhanced antitumour functions of NKG2A + CD8 T cells have been described in previous studies. NKG2A was reported to be a late immune checkpoint and NKG2A expression in CD8 T cells was associated with repeated stimulation and cell division 32, 33 . NKG2A-positive clusters of CD8 T cells in head and neck cancer patients were enriched for other immune checkpoints, including PD-1, TIM-3 and CD39 33 .…”

“…NKG2A was reported to be a late immune checkpoint and NKG2A expression in CD8 T cells was associated with repeated stimulation and cell division 32, 33 . NKG2A-positive clusters of CD8 T cells in head and neck cancer patients were enriched for other immune checkpoints, including PD-1, TIM-3 and CD39 33 . Furthermore, NKG2A + CD8 T cells were characterised by a proliferative, cytotoxic and tissue-resident memory phenotype with TCR-independent functions in bladder cancer 32 .…”

Gamma delta T-cell-based immune checkpoint therapy: attractive candidate for antitumor treatment

“…In γδT cells, NKG2A receptor-mediated inhibitory signaling tends to prevail [ 109 ]. NKG2A+ and NKG2A- cells can be formed from γδT cells during early thymic development and do not appear to change significantly with cell growth [ 110 ], and their expression kinetics are similar to those of cells expressing TIM-3 and CD39, which emerge late but are stably expressed [ 111 ]. The combination of HLA-E with NKG2A, dependent on the participation of ITIMs and SHP1/2, can transmit inhibitory signals to interfere with the activation of γδT cells and limit the function of effector γδT cells.…”

Structure of the murine CD94–NKG2A receptor in complex with Qa‐1b presenting an MHC‐I leader peptide

“…In addition to a role in NK cell immunity, CD94-NKG2A is also expressed by activated/exhausted T cells in response to chronic antigen stimulation [13] or tumour infiltration [14]. Here, CD94-NKG2A limits sustained CD8 + T-cell effector function [3] and can be upregulated under suppressive cytokines such as TGF-b [15,16]. Similarly, HLA-E/Qa-1 b overexpression by tumour cells has been attributed to enhanced tumourigenicity through appropriation of such mechanisms [17].…”