immunoconjugate immunoconjugate immunoconjugates are antibodies conjugated (joined) to a second molecule, usually a toxin, radioisotope or label. these conjugates are used in immunotherapy and to develop monoclonal antibody therapy as a targeted form of chemotherapy when they are often known as antibody-drug conjugates. when the conjugates include a radioisotope see radioimmunotherapy. when the conjugates include a toxin see immunotoxin.