Monoclonal antibodies

Monoclonal antibodies have an increasing role in medicine. They are manufactured by a technique called somatic cell hybridization. This involves the fusion of myeloma cells with spleen cells from a mouse that has been immunized with the desired antigen. The resulting fused cells are termed a hybridoma and act as a 'factory' for producing monoclonal antibodies. The main limitation to this is that mouse antibodies are immunogenic leading to the formation of human anti-mouse antibodies (HAMAs). This problem is overcome by combining the variable region from the mouse body with the constant region from an human antibody.

Clinical examples of monoclonal antibodies:

• infliximab (anti-TNF): used in rheumatoid arthritis and Crohn's
• rituximab (anti-CD20): used in non-Hodgkin's lymphoma and rheumatoid arthritis
• cetuximab (epidermal growth factor receptor antagonist): used in metastatic colorectal cancer and head and neck cancer
• trastuzumab (HER2/neu receptor antagonist): used in metastatic breast cancer
• alemtuzumab (anti-CD52): used in chronic lymphocytic leukaemia
• abciximab (glycoprotein IIb/IIIa receptor antagonist): prevention of ischaemic events in patients undergoing percutaneous coronary interventions
• OKT3 (anti-CD3): used to prevent organ rejection

Monoclonal antibodies are also used for:

• medical imaging when combined with a radioisotope
• identification of cell surface markers in biopsied tissue
• diagnosis of viral infections