Evidence for thymic function in the elderly

The thymus represents the major site of lymphopoiesis of T-cell receptor (TCR) alpha beta T-cells. Age-related involution may affect its potential to reconstitute T-cells that are lost during HIV infection, chemotherapy, and bone marrow transplantation. However, there is mounting evidence that the age-related changes in the thymus are quantitative, not qualitative, and recent data suggest that the adult thymus can indeed contribute to T-cell reconstitution. Using newer methods to assess thymic function, it can be shown that the increases in naive T-cell numbers in patients receiving antiretroviral therapy for AIDS are largely derived from the thymus. This provides direct evidence for the functional capacity of the adult thymus. (C) 2000 Elsevier Science Ltd. All rights reserved.