immune system

  1. Barriers 

Our body has few natural barriers to prevent the entry of pathogens which are given below:

Physical barrier

Physical barriers prevent the entry of germs physically. These include the skin, body hair, cilia, eyelashes, the respiratory tract, and the gastrointestinal tract. These form the first line of defense.

Chemical barriers

We know that our stomach uses hydrochloric acid to break down the food molecules. Due to such a strongly acidic environment, most of the germs that enter our body along with the food are killed before the further process is carried on. Saliva in our mouth and tears in our eyes also have the antibiotic property that does not allow the growth of pathogens even though they are exposed all day.

Cellular barriers

Certain pathogens also manage to enter our bodies. The cells involved in this barrier are leukocytes (WBC), neutrophils, lymphocytes, macrophages, etc. All these cells are all present in the blood and tissues.


Inflammation and fever also work against the germ. The high temperature during fever and inflammation kills the germs.

2. Immune Cells

A cell that is part of the immune system and helps the body fight infections and other diseases.

  1. White Blood Cells 

WBCs are also called leukocytes.  White blood cells are on constant patrol and looking for pathogens. When they find a target, they begin to multiply and send signals out to other cell types to do the same. Our white blood cells are stored in different places in the body, which are referred to as lymphoid organs. These include the following:

  • Thymus — a gland between the lungs and just below the neck.
  • Spleen — an organ that filters the blood. It sits in the upper left of the abdomen.
  • Bone marrow — found in the center of the bones, it also produces red blood cells.
  • Lymph nodes —small glands positioned throughout the body, linked by lymphatic vessels.
  1. Dendritic Cells: Dentric Cells are antigen-presenting cells that coordinate both innate and adaptive immunity. These cells sense the infection and send the message to the rest of the immune system by antigen presentation.
  1. Eosinophils: These contain highly toxic proteins that kill any bacteria or parasite in contact.
  1. Basophils: These attack multicellular parasites. Like the mast cells, these release histamine.
  • Natural Killer Cells: These stop the spread of infections by destroying the infected host cells.
  • Red Blood Cells: The cells in the bloodstream which carry oxygen from the lungs to the tissues.
  • Platelets: Small cells in the bloodstream which are important in blood clotting.

3. Proteins

Protein is vital to build and repair body tissue and fight viral and bacterial infections. Immune system powerhouses such as antibodies and immune system cells rely on protein. Too little protein in the diet may lead to symptoms of weakness, fatigue, apathy, and poor immunity. Some proteins of the immune system are:


Components of the immune system communicate with one another by exchanging chemical messengers called Cytokines. These proteins are secreted by cells.


Interferons (IFN) are cytokines produced during virus infection that are integral for regulating the immune response. Interferon is secreted by cells in response to stimulation by a virus or other foreign substance, but it does not directly inhibit the virus’s multiplication. 


Interleukin (IL) is a group of naturally occurring proteins that mediate communication between cells. Interleukins regulate cell growth, differentiation, and motility. They are particularly important in stimulating immune responses, such as inflammation.  

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