Thymic Function in Amphibians

Abstract

The advantages of using anamniote vertebrates with free-living embryonic stages in studies on the ontogeny of the immune system are well known. Very young larval stages can readily withstand surgical intervention such as that of thymectomy and, unlike mammals, they are exempt from any possible maternal influence. Although experiments on the effect of early thymectomy have recently been reported in fish (1), most results of larval thymus extirpation come from amphibians. This class has many advantages: amphibians adapt well to conditions of laboratory aquaria and vivaria, in many species the early developmental stages are readily obtained and easy to manipulate, good cell markers can be produced by the creation of polyploid forms, inbred strains are available for some species (2) and convenient culture methods have been developed for the study of immune responses in vitro. Two groups which at present are being intensively studied, newts and anuran amphibians, have the additional advantage that the thymus originates in association with a single pair of pharyngeal pouches; in the newts the 5th pouch and in anuran amphibians, pouch 2. This contrasts with apodans, other urodeles and the remaining poikilotherm groups and it obviously facilitates experimental destruction of the thymic buds.