Genesis of Hassall's Corpuscles

Abstract

HASSALL'S corpuscles, a characteristic structure of the thymus, are composed of acidophilic concentrically arranged cells. Only two hypotheses^1,2 for the genesis of these corpuscles account for the epithelioid character of their cells, their extensive branching³, the presence of a lumen at different stages of their development, and the presence of vascular elements within them. If the Hassall's corpuscles have a vascular origin^4,5, this suggests that they are derived from the occlusion of capillary segments followed by inspissation of their contents, and necrosis of the vascular endothelium with proliferation of the neighbouring epithelium to form their typical “onion-like” structure. The other hypothesis^3,6 suggests that Hassall's corpuscles develop from persistent thymopharyngeal ducts lined with epithelium and that the frequent vascular elements are derived from the associated venules. Our evidence—obtained during an investigation of antigen localization in organs—supports the blood vessel origin of Hassall's corpuscles.