Hassall's corpuscles

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Hassall's corpuscles
Minute structure of thymus. Follicle of injected thymus from calf, four days old, slightly diagrammatic, magnified about 50 diameters. The large vessels are disposed in two rings, one of which surrounds the follicle, the other lies just within the margin of the medulla.

A and B. From thymus of camel, examined without addition of any reagent. Magnified about 400 diameters.
A. Large colorless cell, containing small oval masses of hemoglobin. Similar cells are found in the lymph glands, spleen, and medulla of bone.
B. Colored blood corpuscles.
Gray's subject #274 1274
Dorlands/Elsevier c_56/12261097

Hassall's corpuscles (or thymic corpuscles) are structures in the human thymus, composed of epithelial reticular cells. They are named for Arthur Hill Hassall, who discovered them in 1849.

The function of Hassall's corpuscles is currently unclear, and the absence of this structure in the murine thymus has restricted mechanistic dissection. It is known that Hassall's corpuscles are a potent source of the cytokine TSLP. In vitro, TSLP directs the maturation of dendritic cells, and increases the ability of dendritic cells to convert naive thymocytes to a Foxp3+ regulatory T cell lineage. [1][2] It is unknown if this is the physiological function of Hassall's corpuscles in vivo.


  1. * Watanabe N, Wang Y, Lee H, Ito T, Wang Y, Cao W, Liu Y (2005). "Hassall's corpuscles instruct dendritic cells to induce CD4+CD25+ regulatory T cells in human thymus". Nature. 436 (7054): 1181–5. PMID 16121185.
  2. "Old mystery solved, revealing origin of regulatory T cells that 'police' and protect the body"

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