Monoclonal antibodies are produced in laboratories and serve the purpose of enhancing, restoring or mimicing the attack of the immune system on cancer cells. They are made by cloning a specific white blood cell, and all subsequent monoclonal antibodies can be traced back to a unique parent cell. When an antigen is introduced to either a mouse or a rabbit and polyclonal B cells are fused from the spleen to the myeloma, a hybridoma is created. That hybridoma is then cultured in order to continue with antibody production. They can also be designed to have monovalent affinity.