Question

Differentiate between innate immunity and acquired immunity.

Answer 1

Hint: Immunity can be defined as the capability of organisms to counter harmful microorganisms. Our body has developed a system involving various cells and tissues to make us immune to the harmful pathogens. This involves mechanisms that are present since birth along with the ones that we acquire in our lifetime.

Complete answer:
Immunity is the ability of our body to combat the invasion of unwanted pathogens. Based on whether the immunity mechanism is inborn or adapted, immunity is of two types: Innate Immunity and Acquired Immunity.

> Innate immunity refers to immunity mechanisms present in our body since birth. These mechanisms are non-specific and are activated within hours of infection. It is activated by the chemical properties present in the body of the pathogen. The first barrier the pathogen has to breach is our skin. Successful breaching of this basic line of defense activates chemical barriers like anti-microbial secretion of cells, activation of phagocytic cells, dendritic cells or blood protein and the cells that initiate inflammation.

> Acquired immunity is also called specific immunity. This is largely because the cells of the acquired immune response possess the character of ‘specificity’ by virtue of which they are able to recognize specific pathogens and react to them. The mediators of acquired immunity are the lymphocytes and their secreted products called antibodies. The most prominent character of these cells is their ‘memory’, that is once a pathogen is eliminated, the antibodies remember the response activated for that pathogen. In case there is an infection again, the same response system will be activated immediately.

These two types of immunity can be differentiated based on the following points:

Basis of Difference	Innate Immunity	Acquired Immunity
Line of Defense	Innate immunity presents the first line of defense.	It is the second line of defense.
Timeline	Innate immunity is a rapid response.	Acquired immunity is a delayed response.
Cellular components	Natural killer cells, macrophages, complement cells.	Lymphocytes – T and B.
Memory	Not present.	Present.
Specificity	None.	Specific to different pathogens.
Development	Present since birth.	Acquired through the lifetime of an individual.
Distribution	Present in both invertebrates and vertebrates.	Present only in vertebrates.

Note: Immunity is the way our body puts forth defense mechanisms against harmful microorganisms. This is mediated by a first line of defense or the innate immunity that include the cells of our skin, phagocytic cells and natural killer cells. If an invading microorganism manages to breach the initial defenses, a second line of defense is activated, known as the acquired immunity. The mechanism comprises the lymphocytes and their secreted products – the antibodies.