Acts as a negative regulator of innate and adaptive immunity by maintaining immune homeostasis. Plays a regulatory role in the Toll-like signaling pathway by determining the strength of LPS-induced signaling and gene expression. Inhibits TCR-mediated T-cell activation and negatively regulate T-cell function to prevent hyperresponsiveness. Inhibits also autolysosome formation via negatively modulating MTOR activation by interacting with RAC1 and promoting the disassociation of the RAC1-MTOR complex. Plays an essential role in NK-cell biology by acting as a checkpoint and displaying an expression pattern correlating with NK-cell maturation process and by negatively regulating NK-cell maturation and antitumor immunity. Mechanistically, suppresses IL-15-triggered mTOR activity in NK-cells.