Quantification of adrenergic nerve fibers in human thymus at various ages

Adrenergic nerve fibers were studied in human thymus at various ages by bio chemical and morphological methods and by quantitative analysis of images. The whole thymus was harvested during autopsies in prenatal of six months ( n = 6), newborn (n = 6), infant (n = 3), young (n = 3), adult (n = 3) and e lderly (n = 3) men. The thymuses were weighed, dissected and studied. Thymi c slices were subjected to specific staining for the detection of microanat omical details regarding thymic microenvironment and nerve fibers. Histoflu orescence microscopy was used for staining of adrenergic nerve fibers, whil e immunofluorescence microscopy was employed for staining of neuropeptide Y -like immunoreactivity. Biochemical dosage of proteins and of noradrenaline amount was performed. All morphological results were subjected to the quan titative analysis of images. Our results confirmed that many changes occur with age in the whole weight of the thymus and in thymic protein content an d, as a new finding, demonstrated the specific pattern of three independent markers able to characterize sympathetic nerve fibers of the human thymus and its modifications with age: neuropeptide Y-related staining decreases w ith age, whereas the density of adrenergic nerve fibers remains unchanged. The apparent discrepancy among these three independent markers for sympathe tic nerves was discussed.