Tuberculin

Tuberculin is an extract of Mycobacterium tuberculosis, M. bovis, or M. avium that is used in skin testing in animals and humans to identify a tuberculosis infection. Several types of tuberculin have been used for this, of which purified protein derivative (PPD) is the most important. PPD is a poorly defined, complex mixture of antigens. Tests based upon PPD are relatively unspecific since many of its proteins are found in different mycobacterial species.

It is on the WHO Model List of Essential Medicines, the most important medications needed in a basic health system.

Medical uses

The test used in the United States at present is referred to as the Mantoux test. An alternative test called the Heaf test was used in the United Kingdom until 2005, although the UK now uses the Mantoux test in line with the rest of the world. Both of these tests use the tuberculin derivative PPD (purified protein derivative).

History

Tuberculin was discovered by German scientist and physician Robert Koch in 1890. The original tuberculin discovered by Koch was a glycerine extract of the tubercle bacilli and was developed as a remedy for tuberculosis, but it was ineffective in this role. Clemens von Pirquet, an Austrian physician, discovered that patients who had previously received injections of horse serum or smallpox vaccine had quicker, more severe reactions to a second injection, and he coined the word allergy to describe this hypersensitivity reaction. Soon thereafter von Pirquet discovered the same type of reaction took place in those infected with tuberculosis, and he thus found the utility of what would become the tuberculin skin test. Individuals with active tuberculosis were usually tuberculin positive, but many of those with disseminated and rapidly progressive of disease were negative. This led to the widespread but erroneous belief that tuberculin reactivity is an indicator of immunity to tuberculosis.