Differences Between Lymph Node Structure and Function in Normal and Athymic Rats

Abstract

The congenitally athymic, nude mouse strain could hardly have arrived at a more opportune time than in the mid 1960s (Flanagan 1966; Pantelouris 1968). Only a few years earlier neonatally thymectomized mice had been shown to develop immunodeficiency (Miller 1961), the dual nature of the immune system was indicated by studies of chicken lacking either a bursa of Fabricius or both a bursa and thymus (Warner et al. 1962), and lymphocytes had been proven to be the immunocompetent cells of the body (Gowans and McGregor 1965). The selective absence of T cells rendered the nude mouse an invaluable animal model for tumor research and many areas of immunological research. For almost a decade it ruled the ground alone before the nude rat entered the stage. Hairless rats had incidentally been bred at the Rowett Research Institute since 1953, but were apparently not realized to be athymic and were subsequently lost, until they reemerged in the same breeding colony in 1975. This time they were found to be congenitally athymic, and were assigned the symbol rnu (Festing et al. 1978). At about the same time, another nude rat strain, designated nznu, was discovered in New Zealand (reviewed in Festing 1981). Although they arrived late, the role of these athymic rats has not been restricted to duplicating research on the nude mouse. Due to their larger size rats are often better suited than mice for in vivo physiological studies of lymphocytes and other leukocytes. It is also possible that a pleiotropic gene such as rnu will have other functional consequences immunologically than the absence of a thymus.