Immuno-characterisation of neuroendocrine cells of the rat thymus gland invitro and in vivo

Primary cell cultures and organ fragments of rat thymus were characterised by use of a panel of antibodies raised against the neural adhesion molecule L1, tyrosine hydroxylase, protein gene product 9.5, nerve growth factor, c alcitonin gene-related peptide, glial fibrillary acidic protein, vimentin, pan-cytokeratin, a ganglioside of neural crest and neuroendocrine cells (A2 B5), and thymulin (4 beta). Immunoreactivity for neural markers only was id entified in a single morphology (nerve-like) of cell in culture and through out the adult thymus as fine, tortuous staining. Immunoreactivity for endoc rine markers only was identified in polygonal epithelial-like cells in cult ure, throughout viable tissue in fragment culture and in the subcapsular co rtex of the adult thymus. Immunoreactivity for both endocrine and neural ma rkers was identified in three distinct morphologies in cell culture: elonga te, spherical, and stellate. Similar results were observed in the mitotic p eriphery of the cultured fragments and in the medulla and cortico-medullary junction of the adult thymus. Cells with immunoreactivity to A2B5 were pre sent in primary and fragment cultures and occurred throughout the adult thy mus. The apparent diversity of cell immunoreactivity in primary and fragmen t thymic cultures suggests that numerous neural and endocrine factors may b e required for the development and/or regeneration of the thymic microenvir onment.