IgG2  FcγRIIa His131  CH1 of Fab and/or upper hinge  Stable core hinge with additional inter H‐chain disulfide bonds in the upper hinge.  Unstable CH3:CH3  Alternative light‐chain attachment creates distinct conformers. Unlike IgG4, the CH3:CH3 instability does not lead to half‐molecule exchange as a result of stable core and upper hinge disulfides.