Table 4.
Human IgG subclasses and binding affinity to human FcγRs a b
| Fc receptors | IgG1 | IgG2 | IgG3 | IgG4 | |
|---|---|---|---|---|---|
| Activating | FcγRI | High | No binding | High | High |
| FcγRIIaH131 | Medium‐low | Low | Low | Low | |
| FcγRIIaR131 | Medium‐low | Very low | Low | Low | |
| FcγRIIIaV158 | Medium‐low | Very low | High | Low | |
| FcγRIIIaF158 | Low | No binding | High | Low | |
| Inhibitory | FcγRIIb | Low | No binding | Low | Low |
IgG, immunoglobulin.
a
The murine FcγRs that functionally correspond to the human FcγRI (hCD64), FcγRIIa (hCD32a), FcγRIII (hCD16), and FcγRIIb are FcγRI, FcγRIII, FcγRIV, and FcγRIIB, respectively. bC1q binding: IgG3 > IgG1 > IgG2. IgG4 does not bind C1q.