Differential expression of inhibitory receptor NKG2A distinguishes disease-specific exhausted CD8⁺ T cells

Exhausted CD8⁺ T (Tex) cells are caused by persistent antigenic stimulation during chronic viral infection or tumorigenesis. Tex cells upregulate and sustain the expressions of multiple immune inhibitory receptors (IRs). Blocking IRs of Tex cells, exemplified by PD-1, can partially restore their effector functions and thus lead to viral suppression or tumor remission. Tex cells derived from chronic viral infections share the expression spectrum of IRs with Tex cells derived from tumors; however, whether any IRs are selectively expressed by tumor-derived Tex cells or virus-derived Tex cells remains to be learnt. In the study, we found that Tex cells upregulate IR natural killer cell lectin-like receptor isoform A (NKG2A) specifically in the context of tumor but not chronic viral infection. Moreover, the NKG2A expression is attributed to tumor antigen recognition and thus bias expressed by tumor-specific Tex cells in the tumor microenvironment instead of their counterparts in the periphery. Such dichotomous NKG2A expression further dictates the differential responsiveness of Tex cells to NKG2A immune checkpoint blockade. Therefore, our study highlighted NKG2A as a disease-dependent IR and provided novel insights into the distinct regulatory mechanisms underlying T cell exhaustion between tumor and chronic viral infection.