So I looked up serial transplantation all the way back to 1940 and couldn’t find anything. I do remember reading about it and I’m usually right about those things, but the following paper gives the case of the involuted, dysfunctional thymus that regained functionality in a young animal and lasted the rest of its life; so that’s two lifespans (which should top the 120 year limit) – Song, Z., Wang J, Guachalla LM, Terszowski G, Rodewald H-R, Ju
Z, Lenhard RK, Rudolf, K.L Alterations of the systemic environment are the
primary cause of impaired B and T lymphopoiesis in telomere-dysfunctional mice.
Blood 2010; 115(8): 1481–9. It’s an amazing paper for various reasons – I’ll attach it if no one minds. Pretty curious that no one has investigated these effects and yet we perform organ transplants all the time? Maybe they were done before the 1940s? I’d bet Caleb (Tuck) Finch would know.