Immunity
Introduction
The term immunity is derived from the Latin word “immunis” (exempt), which was originally
referred to the protection from legal prosecution offered to the Roman senators
during their tenures in office. This term was adopted subsequently to
des-ignate the naturally acquired protection against diseases, such as measles
or smallpox. It indicated that an individual can develop lifelong resistance to
a certain disease after having con-tracted it only once. The cells and
molecules responsible for immunity constitute the immune system, and their
collective and coordinated response to foreign substances is called the immune
response.
The concept of immunity has existed since the ancient times. An
example is the Chinese custom of making children resistant to smallpox by
making them inhale powders made from the skin lesions of patients recovering
from the disease. The first European mention of immunity is recorded by
Thucydides in Athens during the fifth century BC. In describing plague in
Athens, he wrote in 430 BC that only those who had recovered from plague could
nurse the sick, because they would not con-tract the disease a second time.
Once the concept of existence of immunity was established, it was
not long before manipulation of immunity under con-trolled conditions followed.
First, it was Edward Jenner who in a successful experiment injected the
material from a cowpox pustule into the arm of an 8-year-old boy and
demonstrated the lack of development of disease after subsequent exposure to
smallpox. This was based on his observations that milk-maids who had suffered
from cowpox never contracted the more serious smallpox. Jenner’s technique of
inoculating with cowpox to protect against smallpox spread quickly throughout
Europe. However, for many reasons, including lack of knowl-edge of obvious
disease targets and their causes, it was after nearly hundred years that this
technique was applied to pre-vent smallpox.
The experimental work of Emil von Behring and Shibasaburo Kitasato
in 1890 gave the first insights into the mechanism of immunity, earning von
Behring the Nobel Prize in Medicine in 1901. Von Behring and Kitasato
demonstrated that serum (the liquid, noncellular component of coagulated blood)
from animals previously immunized to diphtheria could trans-fer the immune
state to unimmunized animals. Since then, immunology as a field of study has
come a long way. It has been and remains one of the hottest fields of research
as shown by the statistic that about 17 Nobel Prizes have been awarded to scientists
involved in immunological research.
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