noun, plural: T lymphocytes
Lymphocytes are a type of white blood cells. They may be grouped into two: small and large lymphocytes. The small lymphocytes include B lymphocytes and T lymphocytes. The B lymphocytes are involved in the production of antibodies in the humoral immune response. The T lymphocytes participate in the cell-mediated immune response. The large lymphocytes include the natural killer cells.
T lymphocytes, also called T cells, are a type of lymphocytes responsible for the cell-mediated immunity. The T in T lymphocyte stands for thymus. The thymus is the bodily organ where T lymphocytes mature. They are distinguished from other types of lymphocytes by the presence of special receptor (T cell receptor) on the cell surface. These receptors cannot bind directly to the antigens of the pathogens. Rather, they connect to the antigen presented on the cell surface of infected cells.
Similar to a B lymphocyte (which is another type of lymphocyte), the T lymphocyte is a nonphagocytic cell. Morphologically, both lymphocytes look similar when viewed under a light microscope and therefore are difficult to be identified one from the other. Nonetheless, the cell surface marker for T lymphocyte is CD 3 whereas that for B lymphocyte is CD 19.
The different types of T lymphocytes are as follows:
- T helper cell
- natural killer T cell
- suppressor T cell
- cytotoxic T cell
- memory T cell
- regulatory T cell
- gamma delta T cell
Word origin: French lymphe, from Latin lympha (water, water nymph), from Ancient Greek númphē (nymph) + New Latin cyta, from Ancient Greek kútos (vessel, jar)