The British Medical Journal is launching a competition to decided the greatest medical breakthrough.
Present-day medical experts are championing discoveries from the last 166 years.
Mike Kemeny and Paul MacAry, immunology programme and department of microbiology, National University of Singapore are backing advances in immunology.
Immunology is the study of all aspects of the immune system, the body's defence against infection.
Monoclonal antibodies can be naturally and synthetically produced
It was largely a mystery to scientists until 1958 when French researcher Jean Dausset described the first human histocompatability (HLA) antigen.
HLAs are present on the surface of cells as a "biological signature".
If the body does not recognise this signature, the immune system springs into action.
This is why the body fights infections, and why it is programmed to attack transplanted organs and tissues.
Understanding of the immune system has also fuelled the development of antisera (anti-toxin) treatments, such as that for diphtheria, and of the definition of blood types.
Monoclonal antibodies were another discovery.
These are naturally produced by immune cells, but synthetic versions can be produced, such as those which damp down inflammation in people with rheumatoid arthritis.
Herceptin, the anti-breast cancer drug is a monoclonal antibody.
Dr Kemeny and Dr MacAry say: "It is estimated that a third of all drugs currently being developed by drug companies are monoclonal antibodies, and hence antibody technology will enable many more medical milestones to be reached in the foreseeable future."