Since the pandemic period started, we have been talking and listening about immunity. But having a clear idea about what exactly is immunity is rare. So to get a clear idea about immunity we need to dive into Immunology (study of immune system, immune responses to foreign substance and their role in resisting infections).

Immunity primarily consists of two components –


Any foreign substance invading the body and capable of stimulating an immune response.


Protective chemicals produced by immune cells in response to antigen.

There are some strange characteristics of the immune system.
1. It can differentiate between self and non-self ( own body’s cell and foreign molecules).
2. It possesses memory.
( It can recognize antigen if it is fighting second or third time or maybe again and again with the same antigen).

Every day, thousands of microorganisms invade your body, and hence there is a constant war between these organisms (antigen) and your immune system. All these primarily take place in your blood.

Our blood is composed of mainly three types of cells.
1. RBC ( red blood corpuscles)
2. Platelets ( thrombocytes).
3. WBC ( white blood corpuscles)

Lymphocytes which are a part of WBC are involved in the immune response of the body. These are produced in bone marrow by a process called hemopoiesis. There are trillions of lymphocytes circulating in your body the moment it comes in contact with any foreign( not belonging to the body) organism or particles, it gets sensitized.

Once the lymphocytes get sensitized it’s two components i.e. T lymphocytes and B lymphocytes start working.
The working of T lymphocytes and B lymphocytes is different.


On coming in contact with antigen, t lymphocytes form clones( exact copy) of themselves, it basically produces 4 different types of t lymphocytes which work together to give an immune response.

1. Helper T cells – Helper T cells produces lymphokines which helps in rapid multiplication of T cells and also stimulate B lymphocytes and invites macrophages( special cells which digest foreign particle)
2. Killer T cells- These cells directly attack and destroy the foreign organism. They bind to the infected cell and secrete perforin that produces holes in the cell hence killing it. Therefore they are also known as cytotoxic cells.
3. Suppressor T cell – These cells suppress the entire immune system to make sure it doesn’t attack its own body.
4. Memory T cell – These cells retain the memory of the entire responsibility for the future.
It would not be out of context to mention that killer t cells use different types of tools and chemicals for different antigens. And that’s what makes it important to keep a memory for future encounters with the same pathogen.


B lymphocytes are sensitized by both antigens as well as helper T cells. These cells then make clones of plasma cells and memory B cells. Till now, you must have got an idea about what memory B cells would do. As for plasma cells- they produce a proteinaceous substance known as an antibody. These antibodies circulate along with the blood in the entire body and where ever they find a pathogen (disease-causing organism) they engulf it ( swallow) , after the antibodies engulf the pathogen it remains a harmless immobilized mass which is later digested by macrophage. One of the important functions of antibodies is to neutralize the toxins released by pathogens.

There are also a group of cells ( macrophages+ B lymphocytes+ dendritic cell) that work together and deliver a costimulatory signal that is necessary for helper T cells activation.

It becomes necessary to understand here that the above steps don’t happen in sequence it is rather a series of steps taking place simultaneously. Our body is always in a dynamic state of war against these invading pathogens.

    Written By : Azra Rizwan

You might also like

Leave a Reply

Your email address will not be published. Required fields are marked *