Monday, October 20, 2008


The term immunity indicates the condition of an individual who recovers form a disease and is no longer susceptible to that disease a broader definition of immunity all of the physiological mechanism that give an organism the ability to recognize foreign substances and neutralize or degrade them, with or without injury to the organism’s own tissue. Immunology is branch of medicined concerned with the body’s response to foreign substances.

History of Immunology

In attempt to prevent diseases, 15th- century Chinese practiced the custom inhaling dried powders of smallpox crusts to gain protection, but the inoculation of human smallpox materials was found to be hazardous. Edward Jenner observed that people who cought cowpox rarely contracted smallpox . In 1796 he induced cowpox in a young boy and later tried to infect the boy with smallpox, but the immunity provoked by the cowpox virus was effective against smallpox.

Louis Pasteur discovered in 1879 that neglected cultures of the bacteria that cause chickens chlorella lost much of their ability to cause the disease, whereas fresh cultures failed to infect chicken previously inoculated with old cultures. The introduction of dead or attenuated (weakened) microbes into the body to develop resistance to disease is called Vaccination (from the latin vacca; cow). Vaccination is used against such bacterial disease as cholera, dhphteria, and tetanus, and viral infection including hepatitis B, measles, polymielitis and rabies.

The work of Jenner and Pasteur marked the beginning of the field of immunology. Paul Ehrlich proposed the humoral theory of immunity, emphasizing the role of antibodies, protein produced by cells and released into the bloodstream, as the major agents of immunity. Russian biologist Elie Metchnikoff (1845-1946) developed the body’s scavenger cells, are the major detectors of foreign material and the primary defense system against infectious organisms. Both theory are correct.

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