Monday, July 2, 2007

Immunology - An Introduction

The immune system is a remarkably adaptive defense system that has evolved in vertebrates to protect them from invading pathogenic microorganisms. It is able to generate an enormous variety of cells and molecules capable of specifically recognizing and eliminating an apparently limitless variety of foreign traders.

Functionally, an immune response can be divided into two interrelated activities – recognition and response. Immune recognition is remarkable for its specificity. The immune system is able to recognize subtle chemical differences that distinguish one foreign pathogen from another. At the same time, the system is able to discriminate between foreign molecules and the body’s own cells and proteins. Once a foreign organism is recognized the immune system enlists the participation of a variety of cells and molecules to mount an appropriate response, known as effector response, to eliminate or neutralize the organism. In this way the system is able to convert the initial recognition event into different effector responses, each uniquely suited to eliminate a particular type of pathogen. Later exposure to the same foreign organism includes a memory response, characterized by a heightened immune reactivity, which serves to eliminate the pathogen and prevent disease.

Variolation – dried crusts derived form smallpox pustules were either inhaled into the nostrils or inserted into small cuts in the skin. Edward Jenner in 1798 significantly improved this technique.
Next technique is Vaccination done by Louis Pasteur.
Immunity mediated by antibodies (serum / antigen) contained in body fluids (known at the time as humors) is called humoral immunity.
In 1883, even before the discovery of antibodies, Elie Metchinkoff demonstrated that cells also contribute to the immune state of an animal. He observed that certain white blood cells, which he termed phagocytes, were able to ingest microorganisms and other foreign material. This is called cell-mediated immunity. Both the humoral and cell mediated immunities are interrelated and both were necessary for the immune response. In 1950s the lymphocyte was identified as the cell responsible for both cellular and humoral immunity.

Components of Immunity:
Immunity – the state of protection from infectious disease- has both nonspecific and specific components. Innate or nonspecific immunity refers to the basic resistance to disease that an individual in born with. Acquired or specific immunity requires the activity of a functional immune system, involving cells called lymphocytes and their products. Innate defense mechanisms provide the first line of host defense against invading pathogens until an acquired immune response develops.

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