Therapeutic antibodies are laboratory-engineered substances that recognize and bind onto a protein on the surface of a cell.Each therapeutic antibody recognizes a different protein, or antigen, and in general can be used alone, in combination with chemotherapy or as a carrier of substances such as toxins or radiation.ther naked or unlabeled therapeutic antibodies are used because they attach to certain sites, called receptors, on cancer cells where they signal cancer cells to die (apoptosis) or they can work by blocking other molecules that stimulate the cancer cells' growth from binding to the cancer cell.