Glial fibrillary acidic protein immunoreactivity in human respiratory tract cartilages and pulmonary chondromatous hamartomas

Immunocytochemical investigation was performed on a large series of adult, neonatal, and fetal respiratory tract cartilages to ascertain their immunoreactivity for glial fibrillary acidic protein (GFAP) and vimentin. Two polyclonal and six different monoclonal antibodies were used to document the presence of GFAP-immunoreactive chondrocytes in all the fetal and neonatal cartilages as well as in the adult epiglottis, arythenoids, and lobar, segmental, and subsegmental bronchi. The number of chondrocytes showing GFAP immunoreactivity decreased from fetal life to adulthood. Simultaneous immunoreactivity for GFAP and vimentin has also been ascertained in chondrocytes and in perichondrial stellate or elongated cells of the 25 chondromatous hamartomas investigated. These findings document yet another 'inappropriate' pattern of intermediate filament immunoreactivity in normal and neoplastic human cells, and contradict the widely held supposition that the expression of GFAP is restricted to cells of glial origin.