Immunity

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.