The science behind working of our immune system

A scanning electron microscope image of a single white blood cell (yellow/right), engulfing anthrax bacteria (orange/left) – scale bar is 5 µm (false color)

The immune system is the system of organs and specialized cells that protect an organism from exterior biological influences. (Though in a broad sense, almost every organ has a protecting function – for instance, the stomach’s acidic environment or the tight seal of the skin.) When the immune system functions properly, it protects the body against viral and bacterial infections, destroying foreign substances and cancer cells.

Nearly all breathing organisms have some immune system. Bacteria have a simple immune system in the form of enzymes that defend the body against virus infections. Other primary immune mechanisms evolved in ancient animals and plants and remained in their present-day descendants. These mechanisms include antimicrobial, phagocytosis, peptides called defensins, and the complement system. Jawed vertebrates, including humans, have even more complicated defense mechanisms, including the capacity to adapt to identify pathogens more efficiently. Acquired (or adaptive) immunity creates an immunological memory leading to an enhanced response to following encounters with that same pathogen. This means of acquired immunity is the principle of vaccination.

The main parts of the human immune system are:

  • antibodies
  • white blood cells
  • lymphatic system
  • complement system
  • bone marrow
  • spleen
  • thymus.


Antibodies assist the body in fighting harmful microbes or the poisons (toxins) they produce. They do this by recognizing antigens on the microbe’s surface or in the chemicals they produce, which mark the toxins or microbe as foreign. The neutralizers then mark these antigens for demolition. There are many proteins, cells, and chemicals involved in this offense. 

White blood cells

White blood cells are the principal players in your immune system. They are composed in your bone marrow and are a member of the lymphatic system. White blood cells move through tissue and blood throughout your body, looking for microbes (foreign invaders ) such as viruses, bacteria, fungi, and parasites. When they located them, they propel an immune attack. White blood cells include lymphocytes (such as T-cells, B-cells, and natural killer cells) and many other kinds of immune cells. 

Complement system

The complement system is composed of proteins whose activities complement the work done by antibodies.

Lymphatic system

The lymphatic system is a strong network of fragile tubes throughout the body. The primary roles of the lymphatic system are to:

  • react to bacteria
  • manage the fluid levels in the body
  • deal with cell products that otherwise would result in disease or disorders
  • deal with cancer cells 
  • absorb some of the fats in our diet from the intestine. 

The lymphatic system is comprised of:

  • lymph glands (also called lymph nodes) — which confine microbes white blood cells (lymphocytes).
  • lymph vessels — tubes that carry lymph, the colorless fluid that bathes your body’s tissues and holds infection-fighting white blood cells


The spleen is essentially a blood-filtering organ that removes microbes and slays damaged or old red blood cells. It also makes disease-fighting elements of the immune system (including lymphocytes and antibodies).

Bone marrow

Bone marrow is a crucial spongy tissue found inside your bones. It creates the red blood cells our bodies need to transport oxygen, the white blood cells we use to combat infection, and the platelets we need to ease our blood clots. 


The thymus monitors and filters your blood content. It produces white blood cells, which are also called T-lymphocytes.

These elements combine and operate in unison to immune our body from foreign invaders.

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