Immunity (medical)

In biology, immunity is the balanced state of having adequate biological defenses to fight infection, disease, or other unwanted biological invasion, while having adequate tolerance to avoid allergy, and autoimmune diseases.

It is the capability of the body to resist harmful microorganisms or viruses from entering it. Immunity involves both specific and nonspecific components. The nonspecific components act either as barriers or as eliminators of wide range of pathogens irrespective of antigenic specificity. Other components of the immune system adapt themselves to each new disease encountered and are able to generate pathogen-specific immunity.

The basic premise for the division of the immune system into innate and adaptive components comes down to the innate system being composed of primitive bone marrow cells that are programmed to recognise foreign substances and react, versus the adaptive system being composed of more advanced lymphatic cells that are programmed to recognise self substances and don't react. The reaction to foreign substances is etymologically described as inflammation, meaning to set on fire, while the non-reaction to self substances is etymologically described as immunity, meaning to exempt. The interaction of these two components of the immune system creates a dynamic biological environment where "Health" can be seen as an active physical state where what is self is immunologically spared, and what is foreign is inflammatorily and immunologically eliminated. Extending this concept, "Disease" then can arise when what is foreign cannot be eliminated, or what is self is not spared.

Innate immunity, also called natural or native immunity. This immunity is by virtue of genetic constitutional make-up. It is there in the body without any external stimulation or a previous infection. It is divided into two types:- (a) Non-Specific innate immunity: A degree of natural resistance to all infections in general. (b) Specific innate immunity: This is a natural resistance to a particular kind of germ only. Some races or specific individual do not suffer from certain infectious diseases.

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