(I) Modes of extracellular delivery. Antibody therapies bind to extracellular targets or cell surface targets and execute their functions utilizing their attached therapies (enzyme activity, release of conjugated drugs, activation of prodrugs) or initiating immune activation. (II) Nontraditional mechanisms to transport antibodies into cells. These mechanisms transport antibodies and their attached cargo across the plasma membrane directly into the cytoplasm. For example, ENT2 transports the 3E10 antibody, Fc, or Fv into the cytoplasm by a largely undefined mechanism. (III) Antibody binding to cell surface antigens can lead to receptor mediated endocytosis that promotes delivery of antibody therapies to intracellular targets. (IV) Therapeutic nanoparticles can be coated with antibodies to target the nanoparticles to specific tissues or cell types. ADC: antibody-drug conjugate; AEF/ADEPT: antibody-enzyme fusion/antibody-directed enzyme prodrug therapy.