What are white blood cells?

White blood cells are also called leucocytes. They are one of 4 main components of your blood, along with:

• red blood cells
• platelets
• plasma

What do white blood cells do?

White blood cells are an important part of your immune system. Your immune system detects and deals with infections or foreign molecules that enter your body. Things that cause infection are called pathogens (germs).

What are the types of white blood cells?

There are many different types of white blood cells. Each type has a different role in your immune system.

The main types of white blood cells are:

• neutrophils
• monocytes
• eosinophils
• basophils
• lymphocytes

Neutrophils

Neutrophils are the most common type of white blood cell, and the first cell to respond to an infection. They move to infected areas of your body to engulf and destroy germs such as:

• bacteria
• fungi
• viruses

Monocytes

Monocytes play a similar role to the neutrophils. When monocytes move from your blood to your infected tissues, they are known as macrophages.

They also help your lymphocytes to produce antibodies.

Eosinophils and basophils

Eosinophils and basophils help your body fight infections, particularly those caused by parasites. They also play a role in allergic reactions.

Basophils are also important for preventing blood clots.

Lymphocytes

Lymphocytes control the way your other immune cells function.

There are 2 types of lymphocytes:

1. B-cells
2. T-cells

B-cells make antibodies. These are special proteins that stick to germs. This makes them easier for your other white blood cells to see and destroy.

T-cells trigger your body's immune response. They interact with other white blood cells to alert them to an infection. T-cells can also destroy cells in your body that are infected with a germ.

Special lymphocytes also remember germs. These are called memory cells. If you are infected with the same germ again, the memory cell that recognises it can multiply and make antibodies quickly. This helps your body to deal with the infection faster.

How are white blood cells made?

White blood cells are made in your bone marrow. This is found inside your bones.

How do I keep my white blood cells healthy?

Your body needs different vitamins and minerals for your white blood cells and immune system to work properly. These include:

• vitamin A — found in eggs and fish
• vitamin C — found in fruits and vegetables
• zinc — found in red meat, wholegrain foods and dairy products
• B vitamins

Vitamin B

Vitamin B helps to make new white blood cells. Types of vitamin B are found in foods such as:

• meat
• seafood
• cheese
• eggs
• leafy green vegetables
• beans and peas
• cereals and breads with B vitamins added to them

You can read more about vitamin B and your health.

What are problems involving white blood cells?

An abnormally low or high number of white blood cells might indicate an underlying problem.

Low numbers of white blood cells

If you have too few white blood cells, this is called leukopenia.

If you have too few healthy neutrophils, this is known as neutropenia. It can be caused by:

• a virus such as HIV
• autoimmune diseases
• blood cancers such as lymphoma
• cancer treatment

Too few white blood cells can make you more likely to have infections.

High numbers of white blood cells

If you have lots of white blood cells, this is called leukocytosis. This can be caused by:

• infections
• inflammatory conditions such as rheumatoid arthritis
• allergies
• blood cancers such as leukaemia
• conditions that cause tissue death, such as surgery

Treatments for abnormal white blood cell levels depend on the cause.

Resources and support

For more information on the blood, white blood cells, and your immune system, you can visit:

• The Leukaemia Foundation
• Pathology Tests Explained
• The Australasian Society of Clinical Immunology and Allergy (ASCIA)

You can also call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with 24 hours a day, 7 days a week.