Acetylcholinesterase activity in rat thymus after immunostimulation with interleukin beta.

The occurrence and distribution of Acetylcholinesterase (AChE) activity were examined in the thymus of normal and immuno-stimulated adult and aged rats using biochemical and enzymehistochemical methods. Specific AChE reactivity was found primarily in the arteries and, to a lesser extent, in the veins. Only a small amount of activity could be observed in association with the subcapsular and medullary part of the parenchyma and nerve fibers. Our findings indicate that AChE activity in the rat thymus increases after treatment with interleukin beta. In fact treatment with interleukin beta induces an increase of protein content, of the amounts of AChE biochemically assayed and at the levels of AChE histoenzymatically stained. Furthermore, staining of the different structures of the thymus in treated or untreated rats shows that the significant modifications concern the parenchyma, the structures resembling nerve fibers and the whole thymus, while only small changes are observed in AChE activity located in the walls of arteries, veins and lymphatic vessels.