How Your Blood Fights Infection

In our continued series of articles looking at the importance of understanding your own blood results, let us take a look at white blood cells.

Yes, not all blood is red, white blood cells actually play a hugely important role in our health. Never more so than in the situation we find ourselves in now fighting a pandemic. That is because our white blood cells are the first line of defence against viruses, bacteria, infection, inflammation and parasites.

Understanding our own personal numbers linked to our immune response and our white blood cell health, has never been more important. However, for a long and healthy life, this should be considered a basic aspect of our wellbeing to continuously monitor, not just during a pandemic!

There are five key white blood cells that work together to maintain our immune response.


Neutrophils make up roughly half of the white blood cell population. They are usually the first cells of the immune system to respond to an invader such as a bacteria or a virus. As part of their role as first responders, they also send out signals alerting other cells in the immune system to step up and respond to whatever the problem is.

Produced within bone marrow these cells live for only around eight hours, but around 100 billion of these cells are produced by your body every day.

Decreased levels of neutrophils could be a sign of blood disease, low B12, low folate or chronic infection.

Increased levels of neutrophils could be a sign of bacterial infection, viral infection, measles, mumps or chicken pox.

Lymphocytes (B and T)

Lymphocytes are also very important in the immune system and never more than now as the T Cells are responsible for recognising and killing foreign invaders to the body.

Lymphocyte B Cells are responsible for the killing of infections and, along with T Cells, the recognition and hardwiring of the body’s response to that foreign body. They produce the antibodies that ‘remember’ an infection and stand ready in case your body should be exposed.

B lymphocytes play the main role in the efficacy of most of the current vaccines. However, T lymphocytes are very important in some cases such as tuberculosis and pertussis vaccines.


Eosinophils also play a role in fighting off bacteria and are extremely important in responding to infections with parasites, such as worms. They are, perhaps, best known for their role in producing allergy symptoms when they go overboard in mounting an immune response against something like pollen which is mistakenly believed to be an invader.

These cells account for no more than 5% of the white blood cells in your bloodstream but are present in high concentrations in the digestive tract.


Basophils, accounting for only around 1% of white blood cells, are important in mounting a non-specific immune response to pathogens. These cells are perhaps best known for their role in asthma. When stimulated, these cells release histamine among other chemicals. Often, this reaction can be over-played by the body and we can get a reaction to the histamine response that tends to lead to localised inflammation.


Monocytes are the garbage trucks of the immune system; they account for around 5% to 12% of white blood cells in your bloodstream. Their most important function, amongst others, is to migrate into tissues and clean up dead cells.

Hopefully, you can see that with regular blood testing and understanding our body chemistry, we can make sure that our immune response is as healthy as possible and be in a position to recognise small changes that deserve more exploration.