Immunity can be defined as a complex biological structure that has the capability to protect the body against attacks by foreign bodies and harmful microorganisms. The immunity involves both specific and non-specific components. The non-specific components act as a shield against a wide range of harmful microorganisms irrespective of their antigenic makeup. Whereas, the specific components adapt themselves to the disease encountered by the body and help in the generation of pathogen-specific immunity. White blood cells called leukocytes, phagocytes, and lymphocytes are major components of the immune system. These cells protect the body against harmful microorganisms and diseases.
Immunity is of three types, depending upon how it originates and functions:
- Innate immunity: This is the form of immunity that we have by birth. It acts as general protection by the body. For instance, the skin prevents the entry of germs into the body.
- Adaptive immunity: This type of immunity develops in our lifetime. Adaptive immunity is developed when we are exposed to any disease or when we get ourselves immunized against the diseases with diseases.
- Passive immunity: The immunity which is borrowed from other sources is known as passive immunity. It lasts only for a short time span. For instance, a baby gets immunity against diseases with its mother’s breast milk.