The present invention relates to novel molecules (Fc variants) comprising at least one antigen binding region and an Fc region that further comprises a modified hinge which alters the binding of Fc to one or more Fc ligand (e.g., Fc.gamma.Rs) and/or modulates effector function. More specifically, this invention provides Fc variants that have modified binding affinity to one or more Fc.gamma.R and/or CIq. Additionally, the Fc variants have altered antibody-dependent cell-mediated cytotoxicity (ADCC) and/or complement dependent cytotoxicity (CDC) activity. The invention further provides methods and protocols for the application of said Fc variants particularly for therapeutic purposes.