Immunity (medicine)

Immunity (medicine) is the capability of multicellular organisms to resist harmful microorganisms. This involves both specific and non-specific components. The non-specific components act as barriers or eliminators of a wide range of pathogens irrespective of their antigenic make-up. Other components of the immune system adapt themselves to each new disease encountered and can generate pathogen-specific immunity.

Overview

An immune system may contain innate and adaptive components. The innate system in mammalians, for example, is composed of primitive bone marrow cells that are programmed to recognise foreign substances and to react. The adaptive system is composed of more advanced lymphatic cells that are programmed to recognise self substances and non-self substances and are able to generate a global response to non-self substances.

The immune system is found in all multicellular organisms and is based on a very ancient form of protection. The basic premise of the system is to destroy all foreign substances. The immune system can distinguish between normal and foreign substances; the latter are expressed on the surface of cells and are called antigens. The immune system reacts to antigens by producing antibodies. These antibodies then neutralise the foreign substances.

Innate immunity

Innate immunity, also known as natural or genetic immunity, involves the body's natural defenses that are present at birth. This form of immunity is immediate but non-specific, meaning it doesn't protect against any specific threats. Instead, it serves to protect the body against all threats by providing immediate, but temporary, immune response to infections.

Adaptive immunity

Adaptive immunity, also known as acquired immunity, is immunity that develops with exposure to various antigens. Your adaptive immune system remembers pathogens it has encountered in the past, and produces a stronger and faster immune response when it encounters the same pathogen again.

Passive immunity

Passive immunity is the transfer of active humoral immunity in the form of ready-made antibodies. Passive immunity can occur naturally, when maternal antibodies are transferred to the fetus through the placenta, and it can also be induced artificially, when high levels of antibodies specific to a pathogen or toxin are transferred to non-immune persons through blood products that contain antibodies, such as in immunoglobulin therapy or antiserum therapy.

Disorders of human immunity

Disorders of human immunity can result in autoimmune diseases, inflammatory diseases and cancer. Immunodeficiency occurs when the immune system is less active than normal, resulting in recurring and life-threatening infections. In contrast, autoimmunity results from a hyperactive immune system attacking normal tissues as if they were foreign organisms.

See also

• Immunology
• Vaccination
• Immunotherapy
• Immunodeficiency
• Autoimmunity

References

Immunity (medicine) Resources
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