Immunity is the body’s reistance to invasion by microorganism and damage by foreign subtances. The word immunity is derived from a latin word “Immunitas” which means “freedom from disease”.
There are two main types of immunity.
- Natural or Innate immunity
- Acquired immunity
Natural Immunity
Natural immunity is inherited/transmitted from parents to offspring. it is an in-born immunity.
(i) Blood
In our blood there are white blood corpuscles. They oppose microorganisms and form anti toxins in the body. They have the capacity to fight germs. When germs of any disease enter our body these WBCs put up a fight. If they are strong we are safe but if the germs are stronger then we catch the disease.
(ii) Mother’s milk
Mother’s milk is a gift of God to the child. After delivery there is a yellowish thick secretion from mother’s breast. It is called colostrums. It is a protein substance with the protective quality. It provides immunity to babies.
It has been seen that babies who did not get their mother’s milk in the early days of their life were more susceptible to infections. Another important thing is that the milk goes directly in the baby’s body from mother’s body. There is no contact with air. So no chances of contamination are there.
(iii) Skin
Skin also provides protection as it covers our internal organs and doesn’t allow germs to enter our body.
(iv) Nasal hair
Hair present in the nose blocks the germs from the air to enter our body.
(v) Epithelial layer. Our whole body is covered with epithelial layer which protects us from the germs as it has mucus cells.
Acquired Immunity
The two major ways of achieving acquired immunity are:
(i) By inoculation
(ii) By falling ill once
(i) By inoculation
Dead germs of a disease are injected in the patient’s body. The body immediately produces antibodies. The antibodies provide immunity for that disease. Immunity for typhoid, diphtheria, TB, and measles is achieved with this way.
(ii) By falling ill once
If a person contracts a disease, then antibodies of that particular disease are produced in the body, so chances of getting the same disease again are very low, e.g., chickenpox.
In reference to the above article, natural and acquired immunity can be differentiated based on the following criteria;
- Difference in Definition:
The immunity which is present by birth without having prior exposure to pathogenic microorganisms including bacteria, viruses, fungi and etc is called innate immunity. On the other hand acquired immunity develops only when our body is exposed to any antigenic substance.
- Difference in Other Names:
Innate immunity is also called as natural immunity or in-born immunity but adaptive immunity is the second name of acquired immunity.
- Difference in Specificity:
There is a non specific and limited response induced by innate immunity against pathogens but acquired immunity produces specific type of response such as adaptive immunity against S. Aureus.
Innate immunity is always present but acquired immunity depends on external environment.
- Difference in Prior Exposure:
There is no need to have prior exposure in order to get benefits from innate immunity but it is necessary in case of acquired immunity.
- Difference in Response:
Innate immunity acts as a first line of defense in our body and it has rapid response whenever any pathogenic substance enters but response of acquired immunity is little delayed and generally occurs after 1 to 2 weeks or 5-6 days. Usually the subsequent response is more rapid against the same type of pathogen.
- Difference in Memory Cells:
The cells of innate immunity are unable to memorize the antigens but it is possible in case of acquired immunity as they also posses’ memory cells.
- Difference in Potency:
The response of innate immunity is less potent in comparison to acquired immunity which shows highest potency.
- Difference in Cells:
The components of innate immunity are:
- Physical barriers
- Chemical barriers
- Natural killers cells
- Plasma protein
- Dendritic cells.
The components of acquired immunity are as following:
- Humaral immunity (Mediated by B cells which produce antibodies
- Cell mediated immunity (Mediated by T cells such as T helper cells and cytotoxic cells)
References
- larry Mckane, judy kandel, microbiology essentials and applications, second edition.
- Michael J.Pelczar, Jr. E.C.S Chan, Noel R. Kreig, Microbiology, Published by TataMcGraw Hill publishing company New Delhi, Fifth Edition.
- Joanne M.Willey, Linda M. Sherwood, Christopher J.Woolverton, Prescott, Harley, and Klein’s Microbiology, Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Seventh Edition.
- ananthanarayan, CK Jayaram Paniker, ananthanarayan & Paniker’s text bookof microbiology, Published by orient Longman private limited, Seventh Edition.
- Gerard J. Tortora, Berdell R. Funke, Christine L.Case, Microbiology anintroduction, Published by Benjamin Cummings, Tenth Edition.
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