Siglecs as modulators of macrophage phenotype and function

The sialic acid-binding immunoglobulin-like lectins (Siglecs) are a family of receptors expressed widely on cells of the hematopoietic system. Siglecs recognize terminal sialic acid residues on glycans and often initiate intracellular signaling upon ligation. Cells can express several Siglec family members concurrently with each showing differential specificities for sialic acid linkages to the underlying glycan as well as varied hydroxyl substitutions, allowing these receptors to fine tune downstream responses. Macrophages are among the many immune cells that express Siglec family members. Macrophages exhibit wide diversity in their phenotypes and functions, and this diversity is often mediated by signals from the local environment, including those from glycans. In this review, we detail the known expression of Siglecs in macrophages while focusing on their functional importance and potential clinical relevance.