Table 1.
Ig binding affinity, function, and expression of individual FcRs.
| Receptor | Ig Isotype and Subclass Binding Affinity | Function | Expression | |||
|---|---|---|---|---|---|---|
| Myeloid Cell | Lymphoid Cell | Non-Immune Cell | ||||
| FcγRI | IgG1,2,3,4 | High affinity (IgG1 = IgG3 > IgG4 >>> IgG2) |
Activation | Monocyte, Macrophage, Neutrophil, DC, Mast cell, Eosinophil |
- | - |
| FcγRIIa | Low affinity (H131: IgG3 > IgG1 > IgG2 > IgG4 R131: IgG3 > IgG1 > IgG4 > IgG2) |
Activation/Inhibition | Monocyte, Macrophage, Neutrophil, DC, Mast cell, Basophil, Eosinophil |
T cell | Platelet, Endothelium | |
| FcγRIIb | Low affinity (IgG3 > IgG1 > IgG4 >> IgG2) |
Inhibition | Monocyte, Macrophage, Neutrophil, DC, Mast cell, Basophil, Eosinophil |
B cell, Plasma cell |
- | |
| FcγRIIc | Low affinity (IgG3 > IgG1 > IgG4 >> IgG2) |
Activation | Monocyte, Macrophage, Neutrophil | NK cell | - | |
| FcγRIIIa | Low affinity (IgG3 >> IgG1 > IgG4 > IgG2) |
Activation/Inhibition | Monocyte, Macrophage | NK cell, T cell |
- | |
| FcγRIIIb | Low affinity (IgG1 = IgG3 >>> IgG2 = IgG4) |
Activation | Neutrophil, Basophil, Eosinophil | - | - | |
| FcRn | High affinity (pH ≤ 6.5)/Low affinity (pH 7.4) (IgG4 > IgG1 > IgG3 > IgG2) |
Transcytosis/Recycling | Monocyte, Macrophage, Neutrophil, DC | - | Endothelium, Epithelium | |
| FcεRI | IgE | High affinity | Activation | Langerhans cell, Eosinophil, Mast cell, Basophil, DC, Monocyte |
- | Platelet |
| FcεRII | Low affinity | Activation | Langerhans cell, Monocyte, DC, Macrophage, Eosinophil, | B cell, T cell, NK cell |
Platelet | |
| FcαRI | IgA1,2 | Low affinity (IgA1 = IgA2) |
Activation/Inhibition | Monocyte, Macrophage, Neutrophil, DC, Kupffer cell | - | - |
| FcμRI | IgM | Low affinity (monomeric IgM)/High avidity (pentameric IgM) | NA | - | B cell, T cell, NK cell |
- |
| Fcα/μR | IgA/IgM | High affinity (IgM > IgA) |
NA | Macrophage, DC | B cell | - |
| FcδR | IgD | NA | ||||
| plgR | Dimeric IgA/pentameric IgM | High affinity | Transcytosis | - | - | Endothelium, Epithelium |
DC: dendritic cells, NK cells: natural killer cells, NA: not analyzable.