Neonatal thymectomy identifies two major pools of sessile and recirculating peripheral T cells which appear to be under separate homeostatic control

In this study the role of the thymus in the development of sessile T cell p opulations resident in spleen and lymph nodes (LN) was contrasted with the development of recirculating T cell populations trafficking between blood a nd lymph. Extensive analysis of the composition and the rate of growth of t he secondary lymphoid tissues and recirculating lymphocyte pool coupled wit h neonatal thymectomy revealed that the sessile and recirculating T cell po pulations showed different degrees of thymic dependency and increased in si ze at different rates, suggesting these two populations might be under sepa rate homeostatic control. Neonatal thymectomy also resulted in a much great er depletion of CD8(+) and gamma delta TCR+ T cell subsets compared with CD 4(+) T cells in the sessile and recirculating T cell pools, and greatly red uced the number of T cells homing to peripheral lymph nodes compared with t hose homing to the gut.