Lymphocytes or White Blood Cells: Know Your Body’s Natural Killer Cells Protect You

Natural killer cells refer to lymphocytes or white blood cells that form a part of your innate immune system. However, they share a resemblance with adaptive immune system cells including B-cell and T-cell immunity as they come from the same progenitor [1]. Natural killer cells’ role includes providing the first-line defence against pathogens and cancerous cells. Studies have even found that natural killer cells are capable of developing into long-lasting antigen-specific memory cells against haptens and viruses [2].

These cells constitute 5–20% of circulating blood lymphocytes in humans [3, 4]. Read on to find out the contributions of natural killer cells in protecting your body and learn more about the role they play when it comes to your immunity.

Natural killer cells overview 

Natural killer cells are innate immune cells that show impulsive cytolytic function against physiologically stressed cells including virus-infected cells and tumour cells. They are similar to B-cells and T-cells as they form through common lymphoid progenitor cells. Although natural killer cells develop in bone marrow, they can also form in the liver and thymus. The development of these cells undergoes various stages such as maturation, expansion, and receptors acquisition. First, they go through positive and negative selection to remove self-targeting cells. Then, after maturing, they travel to secondary lymphoid tissues to progress through terminal maturation.

The activity of the natural killer cells is controlled by the stimulatory and inhibitory receptors it possesses. Much like B and T cells, natural killer cells exhibit germline-encoded activating receptors to detect stress-induced or pathogen-derived antigens. Over 20 activating receptors of natural killer cells work to recognize proteins that don’t normally live on a cell’s surface. However, if the inhibitory and stimulatory signals are equal, then the inhibitory signal will override the activating signals. This means that self-cell will not get killed i.e. natural killer cells will not be activated. Again, if the inhibitory signal is low, natural killer cells get activated. Fully matured natural killer cells release lytic granules containing cytotoxic chemicals to kill an infected cell [5].

Functions of natural killer cells 

Below are some important functions of natural killer cells. 

• They control and eliminate both virally infected cells and cancer cells.  
• They distinguish between healthy cells and affected cells. The integrated balance of activating and inhibitory signals helps them recognize and kill target cells. 
• Natural killing cells can acquire functional qualities linked with immunological memory. They can develop into memory cells in both the non-infection state and in response to pathogens. 
• They release cytotoxic granules to naturally kill tumour cells. Natural killer cells work with cytotoxic CD8+ T cells and generate an immune response against viruses and tumour cells [6].  
• Natural killer cells also function as regulatory cells. They influence other cells in the body including DCs, B-cells, T-cells, and endothelial cells [7].
• They can even act as mediators of innate immunopathology in patients with chronic hepatitis B virus infection.
• Natural killer cells support in early control of herpes viruses, in hematopoietic stem cell transplantation, in reproduction, and in eliminating tumours.
• Some reports claim that natural killer cells can also be associated with organ transplants, controlling parasites and HIV infections, autoimmunity, and asthma.

Natural killer cells’ role in immunity 

Natural killer cells are a crucial part of the innate immune system that helps control and eliminate virally infected cells and cancer cells. They are effector lymphocytes that control certain tumours and microbial infections. The importance of natural killer cells can be exhibited in a rare immunodeficiency condition known as a natural killer deficiency. A person who suffers from a lack of natural killer cells is highly vulnerable to viral infections and diseases. This is because infected cells cannot be detected and killed in the absence of natural killer cells.

Furthermore, natural killer cells are capable of developing into immunological memory cells that recognize previously encountered pathogens and act quickly. Natural killer cells were first identified to kill cancer and tumour cells without prior immune sensitization [8]. They kill tumour cells by releasing cytotoxic granules that contain granzyme and perforin.

Boost the function of natural killer cells 

Since these cells are critical to the immune system, it is important to know how to boost their production and efficiency. When it comes to the production of natural killer cells, scientists are still working on seeing if stem cell therapy may be able to increase their numbers. However, recent research has revealed that you can boost their function by consuming probiotics as well as mushrooms, garlic, blueberries and certain supplements like zinc [9]. Apart from this, regular exercise and body massages [10] and proper sleep is also recommended to improve their efficacy.

Now that you know about natural killer cell immune responses and natural killer cells’ role in immunity, do your utmost to keep your overall immune system healthy. Eat more fruits and vegetables, get adequate sleep, and exercise regularly. Another way to keep yourself fit as a fiddle is to book an online doctor consultation on Bajaj Finserv Health proactively, whether it is for a general check-up or to address symptoms. This way, you can speak to reputed doctors near you from the comfort of home and ensure that your immunity continues to protect you.