Thymus

The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells or T lymphocytes mature. T cells are critical to the adaptive immune system, where the body adapts specifically to foreign invaders. The thymus is composed of two identical lobes and is located anatomically in the anterior superior mediastinum, in front of the heart and behind the sternum. Histologically, each lobe of the thymus can be divided into a central medulla and a peripheral cortex which is surrounded by an outer capsule. The cortex and medulla play different roles in the development of T-cells. Cells in the thymus can be divided into thymic stromal cells and cells of hematopoietic origin (derived from bone marrow resident hematopoietic stem cells). Developing T-cells are referred to as thymocytes and are of hematopoietic origin. Stromal cells include epithelial cells of the thymic cortex and medulla, and dendritic cells.

The thymus provides an inductive environment for development of T cells from hematopoietic progenitor cells. In addition, thymic stromal cells allow for the selection of a functional and self-tolerant T cell repertoire. Therefore, one of the most important roles of the thymus is the induction of central tolerance.

Thymus (insect)

Thymus is a genus of hymenopteran insects of the family Eulophidae.

References

Thymus (plant)

The genus Thymus (/ˈtaɪməs/;thymes) contains about 350 species of aromatic perennial herbaceous plants and subshrubs to 40 cm tall in the family Lamiaceae, native to temperate regions in Europe, North Africa and Asia.

Stems tend to be narrow or even wiry; leaves are evergreen in most species, arranged in opposite pairs, oval, entire, and small, 4–20 mm long, and usually aromatic. Thyme Flowers are in dense terminal heads, with an uneven calyx, with the upper lip three-lobed, yellow, white or purple.

Several members of the genus are cultivated as culinary herbs or ornamentals, when they are also called thyme after its best-known species, Thymus vulgaris or common thyme.

Thymus species are used as food plants by the larvae of some Lepidoptera (butterfly and moth) insect species, including Chionodes distinctella and the Coleophora case-bearers C. lixella, C. niveicostella, C. serpylletorum and C. struella (the latter three feed exclusively on Thymus).

Classification

There has been a considerable amount of confusion in the naming of thymes. Many nurseries use common names rather than the binomial name, which can lead to confusion. For example golden thyme, lemon thyme and creeping thyme can all refer to more than one cultivar. There is some confusion over the naming and taxonomy of some species, and Margaret Easter (who holds the NCCPG National Plant Collection of thymes in the UK) has compiled a list of synonyms for cultivated species and cultivars.