The marker that is specific for T Cells and NK Cells is CD2. CD2 is a surface protein that is predominantly expressed on T lymphocytes and natural killer (NK) cells. It plays a significant role in cell adhesion and activation during immune responses. The presence of CD2 helps in the identification of these specific cell types in immunophenotyping and flow cytometry analysis.
In contrast, CD14 is primarily expressed on monocytes and macrophages, making it unsuitable for marking T and NK cells specifically. CD25 is the alpha chain of the interleukin-2 receptor, which is expressed on activated T cells but is not unique to them, as it can also be found on regulatory T cells. CD13, also known as aminopeptidase N, is found on various cell types, including myeloid cells and some epithelial cells, but it is not specific to T or NK cells. Thus, CD2 stands out as the marker that distinctly identifies T cells and NK cells.