Mast cell activation is critical for the development of allergic diseases. Ligation of Sialic acid-binding immunoglobin-like lectins (Siglecs) such as CD33, Siglec-6, -7 and -8 have been shown to inhibit mast cell activation. Recent studies showed that human mast cells express Siglec-9, an inhibitory receptor also expressed by neutrophils, monocytes, macrophages, and dendritic cells.
