Quantification of acetylcholinesterase-positive structures in human thymus during development and aging

Acetylcholinesterase (AChE) localization in the human thymus has been studied by biochemical and morphological methods during development and aging. The occurrence, the amount and the distribution of acetylcholinesterase and the changes with age were examined in 24 human thymuses. The whole human thymus was removed during autopsies in males of the following age-groups: prenatal of six months, new-born, infant, young, adult and elderly. The thymuses were weighed, measured and dissected: the microanatomical details were stained with Eosin-orange, nervous structures were identified by means of Bodian's method. Protein content was determined with biochemical methods. Histoenzymatical and biochemical demonstration of acetylcholinesterase was performed. The morphological results obtained were submitted to quantitative image analysis. Our results show that the thymic microenvironment changes with age; moreover, an increase of acetylcholinesterase-positive structures can be observed with age. Biochemical results are in agreement with morphological results and both are confirmed by the outcome of quantitative analysis of images. Acetylcholinesterase activity in human thymus may play a key role in thymic functions.