The mononuclear cells of the bone marrow mainly comprise lymphocytes (T and B), monocytes, and hematopoietic stem cells. They represent a significant fraction of the cells present in the bone marrow.

Mononuclear cells play a crucial role in the process of hematopoiesis, the formation, and development of blood cells. Hematopoietic stem cells, which are essential for the production of blood cells, are part of the mononuclear cell population. They are often used in bone marrow transplants. A bone marrow transplant, also known as a hematopoietic stem cell transplant, can be used to treat various hematological conditions, such as leukemia, lymphoma, or certain genetic diseases.

Mononuclear cells can be characterized and analyzed using techniques such as flow cytometry, which enables different cell populations to be identified and quantified based on their surface markers.

They play an important role in regulating inflammatory responses. They can differentiate into macrophages, which are involved in phagocytosis and the regulation of inflammation.