Siglec-8 is a lectin specific for 6'-sulfo-sLex and a member of the Ig-superfamily. It is expressed almost exclusively in eosinophils; however, basophils and mast cells can express it to a lower degree. Siglec-8 is a 54 kD transmembranal protein; the extracellular domain has one V-set Ig-like domain and two C2-set domains. The cytoplasmic domain has two immunoreceptor tyrosine-based inhibitor motifs (ITIM) that recruit SH2-family phosphatases after tyrosine phosphorylation. There are reports that siglec-8 inhibits the release of histamine and prostaglandin D2 mediated by the IgEFcR. This molelcule is also involved in the induction of apoptosis.