Immunology is the science which deals with the study of immune system, immune responses to foreign substances and their role in resisting infection.
Types of Immunity:
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1) Innate immunity:
Innate immunity is also called natural immunity. It is present from birth. Innate immunity is the inborn capacity of the body to resist the pathogen.
It does not depend on previous exposure to foreign substances. It is also called non-specific immunity, because it comprises of all those defence elements.
It consists of the following types of barriers:
1) Anatomical barriers:
These barriers prevent entry of the microorganisms into the body. They include skin and mucous membrane. Mucous membrane secretes mucus and the mucus coating of the epithelial lining of the respiratory, gastrointestinal and urinogenital tracts help in trapping microbes entering the body.
2) Physiological barriers:
Physiological barriers like body temperature, pH and body secretions prevent growth of many invading pathogenic micro-organisms.
3) Phagocytic barriers:
These bring about phagocytosis of invding microbes. Phagocytosis is an important mechanism of innate immunity.
4) Inflammatory barriers:
An infections or tissue injury often causes redness, swelling, pain and the production of heat that may result in fever. Such localized manifestation is called inflammatory response.
2) Acquired Immunity:
Ability of the body to defend itself against invading foreign agents like bacteria, viruses, toxins and transplanted tissues is called specific resistance. This resistance or immunity that an individual acquires during life is called acquired immnity.
Types of Acquired immunity:
1) Acquired active immunity:
It is the resistance developed by an individual as a result of an antigenic stimulus of invading pathogens or vaccine. This immune is acquired by activating immune system of the body and results in production of antibodies.
It is of two types:
a) Natural acquired active immunity:
Immunity acquired due to infection is called natural acquired active immunity. It is developed after entry of pathogens in the body.
b) Artificial acquired active immunity:
This immunity is acquired artificially by vaccination. Vaccines contain dead or live but attenuated pathogens or toxoids consisting of microbial components or toxins secreated by the pathogens.2) Acquired Passive immunity:
Passive immunity is acquired when ready-made antibodies are received by the body.
Passive immunity can be acquired either naturally or artificailly.
a) Natural acquired passive immunity:
Before birth maternal antibodies arw transferred from mother to foetus through placenta. After birth antibodies are transffered from mother to infant through colostrum. The antibodies received by child from mother remain in the body for a short time.