ReceptorFc˜RI Fc°RI (CD89) Cell type Binding Structure Macrophages Neutrophils Eosinophils IgG1 108 M–1 2 × 106 M–1 2 × 106 M–1 1) IgG1=IgG3 2) IgG4 3) IgG2 Order of afÿnity Macrophages Neutrophils Eosinophils Platelets Langerhans cells Macrophages Neutrophils Eosinophils B cells Mast cells IgG1 IgG1 IgG1 ITIM ITIM IgG1=IgG3 IgA1=IgA2 NK cells Eosinophils Macrophages Neutrophils Mast cells IgG1 Mast cells Basophils IgE IgA1, IgA2 IgA, IgM Fc˛RII-A (CD32) Fc˛RIII (CD16) Fc˛RI (CD64) Fc˛RII-B2 (CD32) Fc˛RII-B1 (CD32) or Effect of ligation Uptake Stimulation Activation of respiratory burst Induction of killing Uptake Granule release (eosinophils) Uptake Inhibition of stimulation No uptake Inhibition of stimulation Induction of killing (NK cells) Uptake Induction of killing UptakeSecretion of granules Macrophages Eosinophils† Neutrophils Macrophages B cells Eosinophils B cells ˜ ° 72 kDa ° 40 kDa ˜-like domain ° 50–70 kDa ˜or ˝ Fc°/˝RFc˜RII (CD23) ° 45 kDa ˙ 33 kDa ˜ 9 kDa ˜ 9 kDa ° 55–75 kDa ° 70 kDa N lectin domain trimer Degranulation IgE 1) IgG1 2) IgG3=IgG2* 3) IgG4 1) IgG1=IgG3 2) IgG4 3) IgG2 2 × 106 M–1 1) IgG1=IgG3 2) IgG4 3) IgG2 1) IgM 2) IgA 5 × 105 M–1 3 × 109 M–12–7 × 107 M–1 (trimer) 2–7 × 106 M–1 (monomer) 1010 M–1 107 M–1
Fig. 10.38 Distinct receptors for the Fc region of the glycosylphosphatidylinositol membrane anchor without γ chains, different immunoglobulin classes are expressed on different whereas in NK cells it is a transmembrane molecule associated with accessory cells. The subunit structure and binding properties of γ chains. The FcγRII-B1 differs from the FcγRII-B2 by the presence these receptors and the cell types expressing them are shown. All of an additional exon in the intracellular region (indicated by yellow are immunoglobulin superfamily members except FcεRII, which triangle). This exon prevents the FcγRII-B1 from being internalized is a lectin and can form trimers. The exact chain composition after cross-linking. The binding affinities are taken from data on of any receptor can vary from one cell type to another. For human receptors. *Only some allotypes of FcγRII-A bind IgG2. †In example, FcγRIII in neutrophils is expressed as a molecule with a eosinophils, the molecular weight of the CD89α chain is 70–100 kDa.