Question

What role does the immune system play in preventing disease? Give specific examples for the first, second and third lines of defense.

Answer 1

The immune system protects our body from the invasion of harmful foreign matters such as bacteria, viruses,parasites and other microorganisms that are responsible for causing harm and disease when present in our body.They do so as they comprise of a complex system of  cells, tissues, and organs that show their effect only on the cells that are attacked by the foreign microbes and not attacking the healthy tissues.The immune cells function as they move through the bloodstream,lymph system and tissues and always keep an eye to look out for foreign matter that might enetr the body.There exists three line of defense as mentioned below:

1. First line of defense: The first line of defense is usually passive as they do not react with the pathogens nor do they recognise them.Their only role is to act as a physical/chemical barrier to prevent the entry of the foreign matters.These include skin,hair,mucous menbranes, saliva,lysozyme,gastric juice etc.
2. Second line of defense:These include the innate immunity or the non specific defense that target and destroy the microbes as a whole and do not react with the antigens on the foreign microbes.This include the activity of phagocytes ,the complement system and the process of inflammation and fever.
3. Third line of defense:This includes the specific resistance or the acquired immunity in which lymphocytes such as T lymphocytes that directly kill theb foreign microbes or assist the B lymphocytes to secrete antibodies that act with specific proteins present on the foreign microbes known as antigens and destroys them.