Null lymphocytes, also known as null cells or null T cells, are a subtype of lymphocytes that lack the surface markers of both T cells and B cells, making them difficult to categorize as either T or B lymphocytes. These cells play a crucial role in the immune response and are involved in the recognition and elimination of certain types of antigens.
Null lymphocytes are characterized by the absence of cell surface markers, such as CD3, CD4, CD8, and immunoglobulin receptors, which are normally expressed on T and B cells. This feature distinguishes them from other lymphocyte subsets. Despite their lack of these markers, null lymphocytes possess large granular lymphocyte (LGL) morphology and exhibit natural killer (NK) cell activity.
These cells are primarily found in peripheral blood and are responsible for the innate immune response against certain pathogens, particularly viral infections and certain types of cancer cells. Null lymphocytes can directly recognize and kill infected or abnormal cells through the release of cytotoxic substances like perforin and granzymes.
Studies have shown that null lymphocytes are associated with certain autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. They have also been observed to be involved in graft rejection in organ transplantation.
In summary, null lymphocytes are a subset of lymphocytes that lack typical T and B cell surface markers but play a crucial role in the immune response, particularly in defense against viruses and abnormal cells.
