Natural killer cells (NK cells)

The Pathology Dictionary Team
March 7, 2023

What are natural killer cells?

Natural killer (NK) cells are a type of lymphocyte and a part of the body’s immune system. They are called “natural killers” because they do not require prior activation to kill infected or abnormal cells, as opposed to other immune cells, such as T cells and B cells.

What do natural killer cells do?

NK cells are primarily responsible for recognizing and eliminating infected or abnormal cells, such as virus-infected or cancerous cells. They can also detect and destroy cells that have been modified by stress or other cellular changes, making them an important part of the body’s defense against cancer and other diseases.

NK cells target cells that express specific proteins called ligands on their surface. These ligands are typically absent or present at low levels on healthy cells but are highly expressed on infected or abnormal cells, allowing NK cells to distinguish them from healthy cells and kill them.

What types of cancers are made up of natural killer cells?

There are several types of cancers that are associated with natural killer (NK) cells.

Cancers associated with NK cells include:

• NK/T-cell lymphoma: This is a rare type of non-Hodgkin lymphoma that primarily affects NK cells and T cells. It usually starts in the nose and upper respiratory tract but can spread to other parts of the body.
• Aggressive NK cell leukemia: This is an extremely rare and aggressive type of blood cancer that is primarily composed of NK cells. It usually affects adults and has a poor prognosis.
• Chronic lymphoproliferative disorder of NK cells: This is a rare and chronic disorder characterized by the proliferation of NK cells. It can sometimes progress to NK cell lymphoma.

It’s important to note that while these types of cancer are associated with NK cells, they are not always exclusively made up of NK cells. They may also involve other types of cells of immune cells.