The present invention provides for IgG1 molecules with improved characteristics. In particular, substitution mutations are provided that, in combination, facilitate improved placental transfer, improved serum half-life and improved FcRn binding. Substitution mutations are also provided, that in combination, can be used to block FcRn function and thereby increase the clearance rates of other (endogenous or exogenous) IgGs, block placental transport of IgGs and have increased affinity/reduced pH dependence for FcRn binding.