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A representation of the cholera epidemic of the 19th century. For thousands of years mankind has been intrigued with the causes of disease and the concept of immunity. The prehistoric view was that disease was caused by supernatural forces, and that illness was a form of theurgic punishment for "bad deeds" or "evil thoughts" visited upon the soul by the gods or by one's enemies. [8]
The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens , from viruses to bacteria , as well as cancer cells , parasitic worms , and also objects such as wood splinters , distinguishing them from the organism's own healthy tissue .
An individual's immunity can be acquired via a natural infection or through artificial means, such as vaccination. [51] When a critical proportion of the population becomes immune, called the herd immunity threshold (HIT) or herd immunity level (HIL), the disease may no longer persist in the population, ceasing to be endemic. [5] [26]
[4] [16] Killer T cell: Lymphocyte: T cell: T lymphocyte; Lymphocytus T; 8-10 Virus-infected cells; Cancer cells; Recruits and communicates with other types of immune cells [4] [17] Memory T cell: Lymphocyte: T cell: MTC; 8-10 Memorizes the characteristics of the antigens; Triggers an accelerated and robust secondary immune response [4] [18] T ...
Immunology is a branch of biology and medicine [1] that covers the study of immune systems [2] in all organisms.. Immunology charts, measures, and contextualizes the physiological functioning of the immune system in states of both health and diseases; malfunctions of the immune system in immunological disorders (such as autoimmune diseases, hypersensitivities, [3] immune deficiency, [4] and ...
The following outline is provided as an overview of and topical guide to immunology: . Immunology – study of all aspects of the immune system in all organisms. [1] It deals with the physiological functioning of the immune system in states of both health and disease; malfunctions of the immune system in immunological disorders (autoimmune diseases, hypersensitivities, immune deficiency ...
He further formalised the theory in his 1959 book The Clonal Selection Theory of Acquired Immunity. He explained immunological memory as the cloning of two types of lymphocyte. One clone acts immediately to combat infection whilst the other is longer lasting, remaining in the immune system for a long time and causing immunity to that antigen.
The immune system plays an important role in protecting the body against cancer. The immune response to cancer can be categorized into the two main categories as discussed above: innate immunity and adaptive immunity. Innate immunity is the first line of defense against cancer.