Table 1  FcγR responses relevant to therapeutic monoclonal antibodies (mAbs).
FcγR‐mediated mechanism of action  Effector responses  Action  Dominant receptor
Activation  Antibody‐dependent cell‐mediated cytotoxicity  Direct killing of target cell  FcγRIIIa
Antibody‐dependent cell‐mediated phagocytosis, trogocytosis  Direct killing of target cell  FcγRIIIa, FcγRIIa, FcγRI
Antigen presentation  Vaccine‐like immunity post‐mAb therapy  FcγRIIa, FcγRI, FcγRIIIa
Inhibition  Reduce B‐cell proliferation or innate cell activation by antibody complexes  Inhibition of ITAM cell activation (i.e. BCR) or activating‐type FcR (i.e. FcγR, FcεRI, FcαRI). Note that the FcγRIIb must be co‐cross‐linked with the ITAM activating receptor.  FcγRIIb
Sweeping  Internalization  Removal of small immune complexes  FcγRIIb a
Scaffolding  Target agonism or apoptosis  Passive “super‐cross‐linking” of mAb on opsonized target cell, for example, CD40, CD28, CD20, by FcγR on an adjacent cell  FcγRIIb; also FcγRIIa, FcγRI?
BCR, B‐cell receptor; ITAM, immunoreceptor tyrosine activation motif.
a  Activating FcγR can also contribute to removal of complexes.
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