Développement des organes lymphoïdes chez l’Amphibien Urodèle Triturus alpestris Laur.; tolérance des allogreffes après la thymectomie larvaire

Abstract

ABSTRACT The development of lymphoid organs in the urodele amphibian Triturus alpestris Laur.; skin allograft tolerance after larval thymectomy The first part of this work is an attempt to extend anatomical knowledge of lymphoid organ differentiation: thymus, spleen and liver in Triturus alpestris Laur. The purpose of the second part is to compare a first-set allograft reaction in normal adult newts (100% rejection) and the allograft reaction of larval-thymectomized adult newts. Thymectomy was performed on 39 newts in the tenth week of their life at a known stage of their splenic and thymic differentiation. These thymectomized newts were grafted 18 months later with two different adult skin grafts. A daily observation of the 78 grafts showed that larval thymectomy induced 72% of tolerance. However, 11 newts rejected their grafts in the same way as normal adult newts, but with a longer median survival time (36 days instead of 23 or 27 days). In five of these newts, dissection showed one or two functional thymic nodules and the allograft rejection was due to an incomplete larval thymectomy. In the six other newts, one thymic nodule was found, so the rejection was probably because the thymectomy was too late. Triturus alpestris Laur., like other urodeles, has no bonemarrow, and splenic lymphocytes are probably, for the most part, of thymic origin. Lymphocytes first appear in the spleen during ths ninth week of larval life. If thymectomy is performed at the end of the tenth week, splenic differentiation is completed and the spleen may substitute for thymus function in allograft rejection.