Evolution of Vaccination: From Observation to Science
The development of methods for defense against infections underwent two key stages:
- Empirical stage (late 18th century). Edward Jenner, based on careful observation, used cowpox pustule material to vaccinate humans against smallpox. The biological mechanism of the phenomenon was not yet understood at the time.
- Scientific stage (late 19th century). Louis Pasteur scientifically validated the principle of vaccination. He developed the method of attenuation—weakening the pathogen using heat, unfavorable environments, or passage through non-susceptible animals. Through this approach, the microbe loses its pathogenicity while retaining the ability to induce a specific immune response. Pasteur created vaccines against anthrax, chicken cholera, and rabies (the first live attenuated vaccine).
To provide mass assistance to the population, including those injured by animal bites, specialized vaccination stations began to open. The first Pasteur station outside France was established in 1886 in Odessa, Ukraine, through the efforts of Élie Metchnikoff and Nikolay Gamaleya. In 1888, the Pasteur Institute was opened in Paris through public donations.
Founders of Immunology and Their Debate
Understanding how the body fights infections emerged from debates among prominent scientists.
Élie Metchnikoff developed the phagocytic theory. He proved that phagocytosis is a universal biological mechanism ensuring protection against foreign agents (including bacteria) at the cellular level. Metchnikoff also laid the foundations of gerontology and the study of normal microflora.
His opponent was Paul Ehrlich, the author of the humoral theory. Ehrlich believed that the primary role in defense belongs to specific substances in body fluids—antibodies.
Subsequent research proved both scientists right. Modern science recognizes the unity of cellular and humoral defense factors. In 1908, Élie Metchnikoff and Paul Ehrlich jointly received the Nobel Prize.
Development of Immunology in the 20th Century
In the first half of the 20th century, scientists began studying immune responses not directly related to defense against infections:
- Allergy (Hypersensitivity): Delayed-type (R. Koch, 1900) and immediate-type reactions were described. In 1906, Clemens von Pirquet grouped them under the term "allergy."
- Immunological memory: The phenomenon of accelerated antibody production upon re-exposure to an antigen was described (M. Rayski, 1915).
- Tolerance: In the 1950s, Peter Medawar and Milan Hašek discovered the phenomenon of immunological tolerance to antigens.
By the mid-20th century, the study of mechanisms at the molecular and cellular levels began. The structure of immunoglobulins was deciphered, interferons and interleukins were discovered, and lymphocytes were divided into T- and B-systems. During this era, immunology finally established itself as an independent medical discipline with its own goals and classification.