Where are NK cells formed in the body?

Natural Killer (NK) cells originate from the bone marrow, which serves as the primary site for hematopoiesis (the formation of blood cells). In the case of NK cells, they are derived from the common lymphoid progenitor cells located in the bone marrow. These progenitor cells eventually give rise to various types of lymphocytes, including NK cells.

Once formed, NK cells can migrate to various tissues and organs, including the spleen and lymph nodes, where they can play crucial roles in immune surveillance and response. However, the actual process of their formation occurs in the bone marrow. The thymus is primarily involved in the maturation of T lymphocytes, not NK cells.

This understanding of NK cell formation highlights the importance of the bone marrow in the immune system and underscores the distinct pathways through which different immune cells develop and mature.