What is leukemia?
Leukemia is a cancer that starts in blood stem cells. Stem cells are basic cells that transform into different types of cells that have distinct functions.
Blood stem cells become lymphoid stem cells or myeloid stem cells.
Lymphoid stem cells turn into lymphocytes, a type of white blood cell. Lymphocytes help fight infections and destroy abnormal cells. The 3 types of lymphocytes are B lymphocytes, T lymphocytes and natural killer cells (NK).
Myeloid stem cells become red blood cells, granulocytes, monocytes or platelets. Red blood cells carry oxygen to all body tissues. Granulocytes and monocytes are types of white blood cells that destroy bacteria and help fight infections. Platelets form clots in damaged blood vessels to stop bleeding.
As they develop, the blood stem cells become blast cells (blasts), which are immature blood cells. In the case of leukemia, there is an overproduction of blast cells. These blast cells develop abnormally and do not become mature blood cells. Over time, blast cells take the place of normal blood cells, preventing them from performing their tasks. When diagnosed with leukemia, these blast cells may be called leukemic cells.
There are many different types of leukemias. They are first classified according to the type of blood stem cell from which they develop. Lymphoid leukemia (also known as lymphoblastic leukemia) originates in abnormal lymphoid stem cells. Myeloid leukemia (also called myeloblastic leukemia) comes from abnormal myeloid stem cells.
The types of leukemia are then subdivided according to the speed at which the disease develops and evolves. Acute leukemia begins suddenly and develops within a few days or weeks. Chronic leukemia develops slowly over months or even years.
The 4 main types of leukemia are Acute Lymphoblastic Leukemia (ALL), Acute Myeloblastic Leukemia (AML), Chronic Lymphocytic Leukemia (CLL) and Chronic Myeloid Leukemia (CML).
In adults, the most common leukemias are CLL and AML. There are many different subtypes of leukemia.
Anatomy and physiology of blood
The blood consists of a liquid, called plasma, and solid cells. Blood cells are made in the bone marrow. Bone marrow is the soft, spongy substance in the center of the bones.
Structure
In adults, the most active bone marrow is iliac bones, shoulder bones, vertebral bones, ribs, sternum and skull. Immature blood cells found in the bone marrow are called stem cells. Stem cells may also be present in a smaller amount in the bloodstream. They are then called peripheral blood stem cells.
All our blood cells grow from stem cells. The process of developing blood cells is called hematopoiesis. At the very beginning of this process, stem cells begin to grow either to the lymphoid cell line or to the myeloid cell line. In both lines, the stem cells are transformed into blasts, which are still immature cells.
Lymphoid cell line
Lymphoid stem cells become lymphoblasts, which become lymphocytes. Lymphocytes are a type of white blood cell. They are also called leukocytes. Lymphocytes help fight infections and destroy abnormal cells.
Myeloid cell line
Myeloid stem cells become red blood cells, platelets, or certain types of white blood cells. Red blood cells carry oxygen to all body tissues. Platelets form clots in damaged blood vessels to stop bleeding.
Myeloid stem cells develop into 2 different types of white blood cells called granulocytes and monocytes. These white blood cells destroy bacteria and other foreign invaders and help fight infections.
Blood cell development
Function
The main function of blood is to carry nutrients, gases, wastes, cells and hormones. Each type of blood cell has a specific function.
Red blood cells carry oxygen from the lungs to the rest of the body. They also carry the body's carbon dioxide to the lungs so that it is exhaled.
Platelets form clots in damaged blood vessels to stop bleeding.
White blood cells help prevent and fight infections by destroying bacteria, viruses, and other foreign cells or substances.
Types of white blood cells
There are many different types of white blood cells. Each type does a different job.lymphocytes
Lymphocytes make antibodies to fight infections. They are found in the lymph nodes, thymus, spleen, tonsils, adenoids, and bone marrow. They are also present in the lymphatic tissue of other parts of the body, such as the appendix, the small intestine and other structures of the digestive system and the respiratory system.
The 3 main types of lymphocytes are:
B cells that produce antibodies to fight bacteria, viruses and other foreign substances such as fungi;
T cells that fight infections, destroy abnormal cells and control the immune response;
natural killer cells (NK) that attack any foreign cell.
granulocytes
Granulocytes fight infections and become active in response to tissue inflammation. The 3 main types of granulocytes are:
neutrophils are the main cells that fight against infections. They surround and absorb, or ingest, bacteria;
Eosinophils and basophils attack and destroy both parasitic organisms and become active during an allergic reaction.
monocytes
Monocytes help fight infections by turning into cells called macrophages, which absorb foreign invaders like bacteria and dying cell waste.Acute Lymphoblastic Leukemia (ALL)
Acute lymphoblastic leukemia (ALL) is a cancer that starts in blood stem cells. Stem cells are basic cells that transform into different types of cells that have distinct functions.
As they develop, the blood stem cells become blast cells (blasts), which are immature blood cells. In the case of leukemia, there is an overproduction of blast cells. These blast cells develop abnormally and do not become mature blood cells. Over time, blast cells take the place of normal blood cells, preventing them from performing their tasks. When diagnosed with leukemia, these blast cells may be called leukemic cells.
Acute lymphoblastic leukemia is also called acute lymphoid leukemia.
ALT originates in abnormal lymphoid stem cells. It is said to be acute because it develops rapidly.
Of the 4 major types of leukemia that occur in adults, ALL is the least common type. It is the most commonly diagnosed leukemia in young children and affects boys more often than girls.
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