Different age-related effects of thymectomy in myasthenia gravis: role of thymoma, zinc, thymulin, IL-2 and IL-6

Different age-related immune pathogenetic mechanisms in myasthenia gravis ( MG) have been suggested because of restoration after thymectomy (Tx) of alt ered zinc, thymulin (TH) and T-cell subsets exclusively in early-onset pati ents (younger < 50 years), not in late-onset patients (older > 50 years). I n this context interleukin-2 (IL-2), interleukin-6 (IL-6) and thymoma are c rucial because both involved in MG pathogenesis and correlated with acetylc holine receptors (AchRs) Ab production. Moreover, IL-2 and IL-6 are zinc-de pendent, are altered in aging and related with zinc and TH age-dependent de clines. Moreover, zinc is relevant for immune efficiency. In order to confi rm these different age-related pathogenetic mechanisms further, the role of thymoma, zinc, TH, IL-2 and IL-6 is studied in MG patients with generalize d MG with and without thymoma before and 1 month and I year after Tx. The h igh IL-2, IL-6, zinc, and AChR Ab levels observed before Tx are significant ly correlated each other in younger MG patients (< 50 years) independently by thymoma and in older MG patients (> 50 years) with thymoma. No correlati ons exist in older MG patients without thymoma. Thymulin is not correlated with other parameters considered to be both in younger and older MG patient s independently by the thymoma. Thymectomy restores zinc; immune parameters and AChR Ab are exclusively in the younger group, not in the older one. Th ese findings suggest that IL-2 and IL-6, via zinc, rather than TH, may be i nvolved in different age-related pathogenetic mechanisms mainly in early-on set MG. By contrast, thymoma may be involved in MG etiology in late-onset r epresenting, as such, a useful discriminant tool for MG etiology between ea rly and late-onset MG patients. Because autoimmune phenomena may rise in ag ing, a parallelism with altered immune functions during aging is discussed. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.