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Table 1 Summary of human Siglec family members, their expression, functions, similarities and differences

From: The intriguing roles of Siglec family members in the tumor microenvironment

Siglec Protein Expression Sialic Acid(SA) Ligands Properties Function Disease Refs
Siglec-1(CD169) Macrophage,monocytes, mature dendritic cells α2,3 > α2,6 Adhesion Cell–cell interaction Mediates antigen presentation; inhibits the proliferation of tumor-asscociated T cell; affects TAMs' function Cancer,autoimmunity, SLE,infectious disease [8, 18]
Siglec-2(CD22) B cells α2,6 Inhibition B cell differentiation and tolerance Lymphoma, leukemia, SLE, sepsis, RA [8, 19]
Siglec-3(CD33) Myeloid progenitors, macrophage, monocytes, microglia α2,6 > α2,3 Adhesion Inhibition Induces apoptosis; inhibits the killing effect of NK cells; regulates myeloid cell proliferation and differentiation AML, AD [8]
Siglec-4(MAG) Myelin producing cells (Oligodendrocytes, Schwann cells) α2,3 > α2,6 Adhesion Inhibition Adjusts axons Neuro-degeneration [8, 20]
Siglec-5(CD170) Monocytes, neutrophils, B cells, activated T cells α2,3 Inhibition Delivers an anti-inflammatory signal; inhibits immune cell activation GBS infection, neutrophil disorders [8, 20]
Siglec-6(CD327) Trophoblasts, mast cells, B cells, circulating T cells α2,6 Inhibition Decrease cytotoxic functions of effector CD8 + T cells; suppress trophoblast invasivenes Cancer, pre-eclampsia, allergy [8, 21,22,23]
Siglec-7(CD328) NK cells, monocytes, mast cells, platelets, activated T cells α2,8 > α2,6 > α2,3 Binding Inhibition Inhibits the killing effect of NK cells; inhibits inflammatory responses of mast cells and basophils Cancer, HIV infection, allergy [24, 25]
Siglec-8 Eosinophils, mast cells, basophils α2,3 > α2,6 Inhibition Apoptosis Induces eosinophils apoptosis Allergy, asthma [8, 24]
Siglec-9(CD329) NK cells, monocytes, macrophages, dendritic cells, neutrophils, activated T cells α2,3 = α2,6, or sulfated ligands Inhibition Apoptosis Promotes tumor angiogenesis; inhibit the proliferation and activation of TAM,NK cells and neutrophils Cancer, asthma, sepsis, COPD, RA [24, 26, 27]
Siglec-10 B cells, NK cells, monocytes, CD4 + T cells α2,3 = α2,6 Inhibition Bind to CD24 Induces apoptosis; inhibits the proliferation and activation of tumorassociated T cells and TAM Cancer, sepsis, allergy [27, 28]
Siglec-11 Macrophages, microglia α2,8 Inhibition Reduced inflammatory response; inhibits microglial activation Neuro-inflammation, AD [24]
Siglec-14 Monocytes, neutrophils α2,3 Activation, Polymorphism Recognizes bacterial pathogens, elicits pro-inflammatory responses SLE, COPD, GBS infection, [8, 20]
Siglec-15 Osteoclasts, macrophages α2,6 or sialyl-Tn Activation Inhibition Modulation of osteoclast differentiation and bone resorption; immune modulation of tumorassociated T cells and TAM Osteoporosis, cancer [24, 29, 30]
Siglec-16 Macrophages α2,8 Activation, Polymorphism Unkown Schizophrenia [24]
  1. SLE Systemic lupus erythematosus, RA Rheumatoid arthritis, AML Acute myelocytic leukemia, GBS Group B Streptococcus, COPD Chronic obstructive pulmoriary disease, HIV Human immunodeficiency virus, AD Alzheimer's disease