Thymus cell migration: 3HTdR-labeled and theta-positive cells in peripheral lymphoid tissues of newborn mice.

Abstract

During recent years the concept of thymic cell migration, as opposed to intrathymic cell death, has found increasing acceptance (review-1). Combined morphological and autoradiographic studies in newborn mice revealed that during the third day after birth, a fraction corresponding to one third of all lymphoid cells present in the organ at the end of this period is lost without appreciable signs of cell death within the thymus (2,3). Studies on thymic cell migration in newborn mice following local labeling of the thymus with tritiated thymidine indicated that a large majority of lymphocytes present in Peyer’s patches and lymph nodes of 3-day old mice were of thymic origin (4,5). Theta (θ), a cell surface isoantigen, is found mainly in thymus and brain (6). θ-positive cells in the peripheral lymphoid tissues are generally considered to be thymus derived cells (7). Raff and Owen employed cytotoxic anti-θ serum to estimate the proportion of thymus derived cells in the developing peripheral lymphoid tissues of newborn mice (8).