Siglec-8 is also known as SIGLEC8, SAF2, SIGLEC-8, SIGLEC8L and sialic acid binding Ig like lectin 8. Siglec-8 was first identified by CD33 homology screening of ESTs from a cDNA library generated from a patient diagnosed with idiopathic hypereosinophilic syndrome and was originally termed SAF-2 (sialoadhesin family 2). At the tissue level, Siglec-8 mRNA was found to be most highly expressed in lung, PBMCs, spleen, and kidney. Two splice variants of Siglec-8 exist. The initially characterized form contains 431 amino acid residues in total, subsequently, a longer form of Siglec-8, initially termed Siglec-8L. Both forms of Siglec-8 are found in eosinophils and contain a V-set domain with lectin activity and two C2-type Ig repeat domains in the extracellular region.