Identification of filaggrin in Hassall's corpuscle by histochemical and immunohistochemical methods.

The Hassall's corpuscles of man and other mammals have been deeply stained by a histochemical method that demonstrates bound histidine. We have employed a polyclonal anti-filaggrin antibody on thymus sections to verify whether this positivity was due to filaggrin and profilaggrin, its polymeric precursor, like in the skin. The immunohistochemical reaction has confirmed the presence of filaggrin in human Hassall's corpuscles as well as in other species. Different patterns have been obtained for corpuscles at different developmental stages.