Figure 2.

Sialic acid-binding receptors on Natural Killer (NK) cells. Different sialic acid-binding receptors are present on NK cells. (a) NK cells express Siglecs (mostly Siglec-7 and Siglec-9), which bind sialic acids and mediate inhibitory signals. Sialylated tumor cells can exploit these receptors to escape NK cell-mediated killing (b) One particular sialic acid motif, sialyl Lewis^x, is detected by the activating receptors NKp46, NKp44, and NKG2D, leading to NK cell activation. (c) NKG2D usually binds stress-induced ligands like MICA, MICB, and ULPs. Binding of NKG2D to its ligands on tumor cells is reduced when these ligands are sialylated.