Null cell
A null cell is a large agranular lymphocyte that develops inside the bone marrow. Null cells lack the common characteristic surface markers that can be found in mature B-cells and T-cells. They are rapidly stimulated in the presence of pathogens like viruses and attack viral-infected or tumor cells in a non MHC-restricted manner. Null cells make up a small proportion of the lymphocytes that can be found in an organism. The term null cell is no longer commonly used; they are normally referred to as natural killer cells or killer cells.
