NKR-P1A/CD161: A Multifunctional Immune Receptor at the Crossroads of Antitumor Immunity.

The immune response of our body, whether it is directed to infective agents, allergens, or tumors, should support our recovery but can also be dangerous if dysregulated. There are molecular systems that have the role of tuning the immune response, such as activating and inhibitory receptors and co-stimulatory molecules. Among this plethora of receptors, immune-checkpoint receptors (ICRs), as well as natural killer receptors (NKRs), expressed on NK and/or T cells can up- or downregulate the function of activating and inhibitory receptors during immune cell crosstalk. Among NKRs, NKRP1A/CD161 has shown to be a promising target molecule for immunotherapy. This receptor showed inhibiting or co-stimulatory effects depending on the cell type analyzed as well as the analytical procedures, reagents used, and the experimental context. The aim of the following review will be to explore the structural and functional features of this receptor on immune cells, its relevance in the tumor microenvironment and its targeting as an immunotherapeutic tool in cancers.