[Immunology in the 20th century--progress made in research on infectious and immunological diseases]

The new era of the modern medicine was opened 100 years ago by Robert Koch and Louis Pasteur who demonstrated that various infectious diseases were caused by their respective microbes. Koch discovered Mycobacterium tuberculosis, the causative agent of tuberculosis. The first breakthrough in the modern medicine to combat against infectious diseases was the discovery of anti-diphtheria toxin antibody by E.A. von Behring and S. Kitasato. The concept of immunity--immune from disease--has thus been established. The immune response between antigen and antibody sometimes provides the host with a harmful effect. The concept of allergy was introduced by Richet and later by Prausnitz and Küstner. Why the same immune response leads to the different outcome, immunity or allergy had not been made clear until the discovery of IgE by Drs. Kimishige and Teruko Ishizaka in 1968: The IgG antibody plays a role in immunity whereas IgE antibody is involved in allergy. Tuberculin skin reaction which is well known as the diagnostic tool for mycobacterial infection was studied by M. Chase in 1945 demonstrating that it was able to be transferred to the healthy individual by immune cells but not by antibody. The immune response is now categorized into two; soluble immunity--immediate type allergy and cell-mediated immunity--delayed type allergy. The rapid progress in the molecular biology in the past decades has also accelerated the progress in immunology, several of which include discovery of two types of lymphocytes; T and B cells; concept of two T cells; Th1 and Th2 cells; and the discovery of cytokines which regulate immune cell responses. The mechanism of the immune response is now understood at the gene level. Several immunological diseases can now be successfully treated by controlling the levels of cytokines involved. For example, refractory rheumatoid arthritis is now under control by the administration of recombinant soluble TNF receptor molecules to the patients. The complete human genome sequence is currently under investigation. We can now envisage the advent of the days when every disease can be diagnosed and intervened at the gene level.