Leukaemia is a cancer of the bone marrow. It affects the cells in the bone marrow that produce white blood cells. The four main types of leukaemia are acute lymphoblastic (ALL), acute myeloid (AML), chronic lymphocytic (CLL) and chronic myeloid (CML). Each type has its own characteristics and treatment.

 

Bone marrow is a spongy material that fills some of the bones and produces stem cells, which develop into the three different types of blood cells:

 

>red blood cells, which carry oxygen to all cells in the body

 

>white blood cells, which are essential for fighting infection

 

>platelets, which help the blood to clot and control bleeding.

 

All these cells normally stay inside the bone marrow until they are mature enough to perform their functions properly. They are then released into the bloodstream so that they can move around the body in the blood.

 

White blood cells

There are two main types of white blood cell: lymphocytes and myeloid cells (also known as granulocytes). These cells work together to fight infection. As some myeloid cells and some lymphocytes only live for a few days, the bone marrow is constantly making new cells to replace the old ones in the blood. The bone marrow normally makes millions of blood cells every day.

 

When they are mature enough to leave the bone marrow, the white blood cells are released into the bloodstream to circulate around the body. Lymphocytes, unlike the myeloid cells, also circulate in the lymphatic system.

 

Lymphatic system

The lymphatic system is one of the body’s natural defences against infection. It is made up of a collection of small lymph nodes (sometimes called glands) which produce lymph, a milky-looking fluid containing lymphocytes. The lymph nodes are found mainly in the neck, armpit and groin and are connected by a network of tiny lymphatic vessels. The tonsils, liver, spleen (which breaks down old blood cells) and bone marrow also contain lymphocytes.

 

What is Acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia is a rare type of cancer, affecting approximately 200 adults per year in the UK. Leukaemia is a cancer of the white blood cells. Normally, white blood cells grow and divide in an orderly and controlled way but in leukaemia the process gets out of control and the cells divide too quickly, but do not mature.

The cell structure of ALL

 

In acute lymphoblastic leukaemia there is an overproduction of immature lymphocytes, called lymphoblasts (sometimes referred to as blast cells). There are two different types of lymphocytes: B-lymphocytes and T-lymphocytes. These immature cells fill up the bone marrow and stop it from making blood cells properly. As the leukaemia cells do not mature, they cannot do the work of normal white blood cells, which leads to an increased risk of infection. Because the bone marrow is overcrowded with immature white cells it cannot make enough healthy red cells and platelets.

 

ALL occurs more frequently in children (under 15 years of age) than adults. When it occurs in teenagers or adults, ALL is more common between the ages of 15–25 and in older people. It is slightly more common in males than in females.

 

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