Subclass | IgG1 | IgG2 | IgG3 | IgG4 |
% of total IgG | 60 to 70 | 20 to 30 | 5 to 8 | 1 to 4 |
Heavy chain | gamma1 | gamma2 | gamma3 | gamma4 |
Heavy chain constant components (CH) | CH1, CH2, CH3 | CH1, CH2, CH3 | CH1, CH2, CH3 | CH1, CH2, CH3 |
MW | 150 kD | 150 kD | 150 kD | 150 kD |
Half-life (days) | 21 to 24 | 21 to 24 | 7 to 8 | 21 to 24 |
Ability to activate classical complement pathway | ++ | + | +++ | – |
Important in antibody response to: | ||||
Proteins | ++ | ± | ++ | ++ |
Polysaccharides | – | +++ | ± | ± |
Allergens | – | – | – | ++ |
Fc-gamma-receptor binding | I, II, III | II | I, II, III | I, II |
Placental transport | ++ | + | ++ | ++ |