The lymphoid tissues in mice with congenital aplasia of the thymus.

The lymph nodes, spleens and Peyer's patches from seven mutant mice with agenesis of the thymus were compared with similar tissues from eight phenotypically normal littermate controls. In all lymph nodes examined from the mice the thymus-dependent areas were virtually `empty' of lymphocytes. In the corresponding areas in the spleen and Peyer's patches the numbers of lymphocytes were also significantly reduced. The mice are potentially important as experimental tools in delineating the role of the thymus in the development of the lymphoid system, and as an experimental model of thymic alymphoplasia in the human.