What is an Immune System?

An immune system can be termed as a remarkable flexible defense system that has evolved to defend animals from invading pathogenic micro-organisms and cancer. It is able to produce an enormous diversity of cells and molecules that are capable of specifically recognizing and eliminating an actually limitless variety of foreign invaders. These cells and molecules work together in a vibrant network whose complexity contends that of the nervous system.

The function
Functionally, an immune response can be divided into two associated activities—recognition and response. Immune recognition is notable for its specificity. The immune system is proficient to recognize fine chemical differences that discriminate one foreign pathogen from another. Furthermore, the system is proficient to differentiate between foreign molecules and the body’s own cells and proteins. Once a foreign organism has been acknowledged, the immune system employees a variety of cells and molecules to mount an apt response, called an effector response, to eliminate or neutralize the organism. In this way the system is able to renovate the initial recognition event into a range of effector responses, each uniquely suited for eliminating a particular type of pathogen. Later exposure to the same foreign organism provokes a memory response, regarded as by a more rapid and finely tuned immune reaction that serves to get rid of the pathogen and thwart disease.

Innate Vs Adaptive Immunity
Substantiation for the occurrence of very plain immune systems in certain invertebrate organisms then gives an evolutionary viewpoint on the mammalian immune system. Elements of the primitive immune system continue in vertebrates as innate immunity along with a more exceedingly evolved system of precise responses termed adaptive immunity. These two systems work in tandem to provide a high extent of protection for vertebrate species. Finally, in some conditions, the immune system fails to act as guardian because of some insufficiency in its components; at other times, it becomes an assailant and turns its splendid powers against its own host.

Variolation
The discipline of immunology was born out of the observation that individuals who had recovered from assured infectious diseases were thereafter sheltered from the disease. Perhaps the earliest written record to the observable facts of immunity can be traced back to Thucydides, the great historian of the Peloponnesian War, who, in his description of a plague in Athens, wrote in 430 BC that those who had just recovered from plague could look after the sick because they themselves would not contract the disease a second time. Although early societies recognized the phenomenon of immunity, almost two thousand years passed before the concept was successfully converted into medically effective practice. The first documentation of the attempts to induce immunity consciously was performed by the Chinese and Turks in the fifteenth century. An assortment of reports suggests that the dried crusts obtained from smallpox pustules were either inhaled into the nostrils or inserted into small cuts in the skin. This technique is referred to as variolation.

Also In 1718, Lady Mary Wortley Montague, the wife of the British ambassador to Constantinople, observed the constructive effects of variolation on the native population and had the practice performed on her own children. This technique was appreciably improved by the English physician Edward Jenner, in 1798.

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