Question

How do cellular barriers and cytokine barriers provide innate immunity in humans?

Answer 1

Hint: Innate and Acquired are two types of immunity seen in the humans. Innate immunity prevents the entry of pathogens and if entered prevents its multiplication. Acquired immunity prepares the body for further attack.

Complete answer:
The word ‘immunis’ means exempt. Immunity is the resistance of the body against infection. If immunity fails, a person can contract any disease and this is known as susceptibility. The study of immunity is immunology.

There are two types of immunity. Innate and Acquired.Innate immunity is the immunity present since birth. This is non-specific and its main function is to protect the body from any kind of pathogen. This immunity includes many barriers. These barriers are
>Physical
>Physiological
>Cellular
>Cytokine

a) Physical barriers: The corneum layer of skin is the main physical barrier. This prevents the entry of pathogens. The mucous membrane lining the alimentary and respiratory tract also traps the pathogens and prevents its entry.

b) Physiological barriers: These are chemicals present in the physiological systems. These include HCl in stomach, lysozyme in tears and saliva, acid in vagina, etc. These also kill the pathogens.

c) Cellular barriers: These are the main defence cells in the body. These are neutrophils,monocytes, macrophages, Nk cells.
>Neutrophils: These are types of WBC’s. These are phagocytic in nature. These are numerous in number and also known as PMN’s (Polymorphonuclear lymphocytes).
>Monocytes: These are the largest type of WBC.
>Neutrophils and Monocytes attack pathogens by amoeboid movement.
>Macrophages: The above two types of cells are circulating in the blood. If the pathogen accidently survives in the bloodstream, it will enter the tissues and start multiplying. The Macrophages are present in the tissues to kill such pathogens. The Monocytes circulate in blood for 8 hrs and then increase in size and leave the blood and transform into Macrophages. These can be wandering or fixed in nature. Examples of macrophages are Kupffer cells in the liver, Alveolar Macrophages in lungs, Microglial cells in the brain, etc.

d)NK cells: These are Natural killer cells. These are formed from lymphoid tissue. These kill the pathogens by two mechanisms
>Perforins: These cells attack the pathogens and create pores in their cells. Thus the water enters the cell, and bursts and the pathogen dies.
>Autophagy: The NK cells kill pathogens by killing themselves.

Cytokine barriers:These are proteins released by the cells that also help to destroy the Pathogens. These proteins are
>Interferons: These are released by WBC’s. These interfere with the viral replication and thus prevents its multiplication. (interfere - interferon)
>Interleukins: These are also released by Leukocytes and prevent the growth of foreign substances.
>TNF: This is Tumor Necrosis Factor. This is released to kill the cells that are cancerous in nature.

Note: The main difference between Innate and Acquired is that innate is non-specific and acquired is specific. Innate only protects the body but Acquired prepares the body for further infections because in Acquired, the memory cells are formed.