Hassall's corpuscles

Hassall's Corpuscles

File:Hassall's corpuscles (1) Case 01.jpg

Hassall's corpuscles (stained pink), surrounded by lymphocytes in a thymic lobule.

Hassall's corpuscles or thymic corpuscles (named after Arthur Hill Hassall) are structures found in the medulla of the human thymus and mouse thymus, as well as in other animals including birds, reptiles, and some mammals. They are composed of concentric layers of epithelial cells, and appear as spherical bodies in a histological section.

Structure

Hassall's corpuscles are composed of a central mass, consisting of one or more granular cells, and a capsule formed of epithelioid cells. They vary in size from 25 to 150 μm in diameter. They are most numerous in the medulla, but are also found in the cortex. They are not found in the thymus of the newborn, and are rare in the young child. They increase in number and size with age, and may disappear entirely in old age.

Function

The function of Hassall's corpuscles is not entirely clear. They are thought to play a role in the maturation of T cells in the thymus. Some researchers believe that they may function as a site of degeneration of useless cells, or as a site of production of certain types of cytokines, such as thymic stromal lymphopoietin (TSLP), which is involved in the development of regulatory T cells.

Clinical significance

Abnormalities in the number or structure of Hassall's corpuscles can be a sign of diseases such as myasthenia gravis, thymoma, or DiGeorge syndrome. In these conditions, the thymus may be underdeveloped or overactive, leading to a decrease or increase in the number of Hassall's corpuscles.

History

Hassall's corpuscles were first described by the British physician Arthur Hill Hassall in 1846. Hassall was studying the thymus gland when he noticed these distinctive structures, which he initially thought were a type of gland. He later realized that they were a normal part of the thymus and named them after himself.

See also

• Thymus
• T cell
• Arthur Hill Hassall

References

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