The role of the thymus and recent thymic migrants in the maintenance of the adult peripheral lymphocyte pool

Berzins, SP; Boyd, RL; Miller, JFAP

Author(s): Berzins, SP; Boyd, RL; Miller, JFAP;
Details: Publication Year 1998-06-01,Volume 187,Issue #11,Page 1839-1848
Journal Title: JOURNAL OF EXPERIMENTAL MEDICINE
Publication Type: Journal Article
Abstract: The thymus is essential for the initial seeding of T cells to the periphery, but its role in maintaining the adult T cell pool remains poorly defined. We investigated whether changes to the rate of T cell export could form part of the mechanism(s) controlling the homeostatic regulation of the size and composition of the peripheral T cell pool. Using neonatal thymi grafted under the kidney capsule, we found that irrespective of whether the pool was oversupplied (by thymic grafts) or undersupplied (due to neonatal thymectomy), the thymic export rate was constant from both the host and graft thymus, and the periphery remained constant in size. Recent thymic emigrants (RTE) were also tracked to determine the extent of their acceptance into the T cell pool of a normal mouse. As a population, RTE are phenotypically mature, but were distinct from resident T cells in the periphery, being released in a CD4/CD8 ratio approximately twice that of established peripheral T cells. This export ratio is similar to that of T cells in the mature thymic compartment, but soon after entry into the periphery, the ratio tills, indicating separate thymic and peripheral regulation of the CD4/CD8 ratio. RTE may also be preferentially incorporated into the periphery, causing displacement of resident T cells, thus maintaining the size of the peripheral pool. Although not vital for the maintenance of a functional T cell pool, the acceptance of RTE in a "full" peripheral pool would ensure that the T cell receptor repertoire is kept diverse and that the T cell population encompasses a broad range of naive as well as memory T cells.
Publisher: ROCKEFELLER UNIV PRESS
Keywords: T-CELLS; HOMEOSTATIC REGULATION; IMMUNE-SYSTEM; MEMORY; EXPANSION; INVIVO; NAIVE; MICE
Publisher's Version: https://doi.org/10.1084/jem.187.11.1839
Terms of Use/Rights Notice: Refer to copyright notice on published article.

Creation Date: 1998-06-01 12:00:00