Siglecs: A Journey Through the Evolution of Sialic Acid-Binding Immunoglobulin-Type Lectins

Dev Comp Immunol. 2018 Sep;86:219-231. doi: 10.1016/j.dci.2018.05.008. Epub 2018 May 8.


Siglecs (sialic acid-binding immunoglobulin-type lectins) are a family of immune regulatory receptors predominantly found on the cells of the hematopoietic system. A V-set Ig-like domain mediates the recognition of different sialylated glycoconjugates, which can lead to the activation or inhibition of the immune response, depending on the involved Siglecs. Siglecs are categorized into two subgroups: one including all CD33-related Siglecs and the other consisting of Siglec-1 (Sialoadhesin), Siglec-2 (CD22), Siglec-4 (myelin-associated glycoprotein, MAG) and Siglec-15. In contrast to the members of the CD33-related Siglecs, which share ∼50-99% sequence identity, Siglecs of the other subgroup show quite low homology (approximately 25-30% sequence identity). Based on the published sequences and functions of Siglecs, we performed phylogenetic analyses and sequence alignments to reveal the conservation of Siglecs throughout evolution. Therefore, we focused on the presence of Siglecs in different classes of vertebrates (fishes, amphibians, birds, reptiles and mammals), offering a bridge between the presence of different Siglecs and the biological situations of the selected animals.

Keywords: ITAM; ITIM; Lectin; Sialic acids; Siglecs; Vertebrate evolution.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Evolution, Molecular
  • Immunoglobulins / genetics*
  • Immunoglobulins / metabolism
  • Lectins / genetics*
  • Lectins / metabolism
  • Phylogeny
  • Sequence Alignment
  • Sialic Acid Binding Ig-like Lectin 3 / genetics
  • Sialic Acid Binding Ig-like Lectin 3 / metabolism
  • Sialic Acid Binding Immunoglobulin-like Lectins / genetics*
  • Sialic Acid Binding Immunoglobulin-like Lectins / metabolism
  • Sialic Acids / metabolism*
  • Vertebrates / genetics
  • Vertebrates / metabolism


  • Immunoglobulins
  • Lectins
  • Sialic Acid Binding Ig-like Lectin 3
  • Sialic Acid Binding Immunoglobulin-like Lectins
  • Sialic Acids