Natural killer (NK) cells patrol the body to detect and eliminate transformed or virus-infected cells. They express a variety of activating and inhibitory receptors that regulate their activity. Inhibitory receptors, such as KIRs, LILRs, Ly49, and CD94-NKG2A, prevent NK cells from attacking healthy cells by signaling through ITIM motifs, which recruit phosphatases like SHP-1, SHP-2, and SHIP-1 to suppress NK cell responses. Activating receptors, such as ITAM-bearing NK receptors, NKG2D-DAP10 complexes, and CD244, trigger NK cell activation through signaling pathways involving ITAMs, which recruit kinases like Syk and ZAP-70. These pathways lead to cytoskeletal rearrangements, degranulation, and cytokine production. The interplay between inhibitory and activating receptors determines NK cell responses. NKG2D-DAP10 complexes are crucial for recognizing stress-induced ligands, while CD244 can act as an activating or inhibitory receptor depending on the adaptor proteins involved. CD244 signaling involves interactions with SH2 domain-containing adaptors like SAP, EAT-2, and ERT, which can either enhance or suppress NK cell activity. The regulation of NK cell signaling is complex and influenced by the density of receptors and their ligands on NK cells and target cells. Understanding these mechanisms is essential for elucidating NK cell function in health and disease.Natural killer (NK) cells patrol the body to detect and eliminate transformed or virus-infected cells. They express a variety of activating and inhibitory receptors that regulate their activity. Inhibitory receptors, such as KIRs, LILRs, Ly49, and CD94-NKG2A, prevent NK cells from attacking healthy cells by signaling through ITIM motifs, which recruit phosphatases like SHP-1, SHP-2, and SHIP-1 to suppress NK cell responses. Activating receptors, such as ITAM-bearing NK receptors, NKG2D-DAP10 complexes, and CD244, trigger NK cell activation through signaling pathways involving ITAMs, which recruit kinases like Syk and ZAP-70. These pathways lead to cytoskeletal rearrangements, degranulation, and cytokine production. The interplay between inhibitory and activating receptors determines NK cell responses. NKG2D-DAP10 complexes are crucial for recognizing stress-induced ligands, while CD244 can act as an activating or inhibitory receptor depending on the adaptor proteins involved. CD244 signaling involves interactions with SH2 domain-containing adaptors like SAP, EAT-2, and ERT, which can either enhance or suppress NK cell activity. The regulation of NK cell signaling is complex and influenced by the density of receptors and their ligands on NK cells and target cells. Understanding these mechanisms is essential for elucidating NK cell function in health and disease.