Which cell surface marker is NOT present on NK cells?

Natural killer (NK) cells are a vital part of the innate immune system, primarily involved in the recognition and destruction of virus-infected cells and tumor cells. The specific cell surface markers that characterize NK cells include CD16 and CD56, both of which play essential roles in their functionality.

CD16 is a receptor that allows NK cells to mediate antibody-dependent cellular cytotoxicity (ADCC). When antibodies bind to target cells, NK cells that express CD16 can recognize and kill those cells effectively. CD56 serves as a marker for NK cells and is involved in cell adhesion and the regulation of cytokine release, highlighting its role in immune responses.

In contrast, CD3 is a marker associated with T cells and serves as part of the T-cell receptor complex. Since NK cells are part of a different lineage and do not express CD3, this distinguishes them from T lymphocytes. Similarly, while CD8 is a marker typically found on cytotoxic T cells that aids in recognizing MHC class I molecules, it is not a marker for NK cells.

Thus, the absence of CD3 on NK cells confirms that this particular cell surface marker is not characteristic of these immune cells, making it the correct choice in identifying which marker is not present on