Antibody molecule. Molecular structure of a monoclonal human immunoglobulin (IgG2a). IgG antibodies are composed of 2 long heavy chains and 2 shorter light chains. This antibody adopts a T-shape: the arms of the T make up the Fab or antigen binding region, while the base part or Fc region plays a role in interacting with the immune system. Atoms are represented as sticks and ribbons and are rainbow-colour-coded. Uner the name of Denosumab this type of human monoclonal antibody is used for the treatment of osteoporosis, treatment-induced bone loss and bone metastases. Medication trade names include Prolia and Xgeva.