AGE-RELATED PROPENSITY TO PERIPHERAL EXPANSION OF V-GAMMA-3(-DELTA(+)T-LYMPHOCYTES AFTER IRRADIATION AND BONE-MARROW TRANSPLANTATION() GAMMA)

The age-related decline in T cell functions is generally considered to be due to changes in the responding alpha beta T cell populations as a result of impairment of T cell differentiation in the thymus. T cell s bearing the gamma delta TCR are normally a minor subset of circulati ng T cells, but often the major T cell type among lymphocytes in epith elial tissues. In this paper we show that gamma delta T cells are expa nded in lymph nodes of irradiated mice after syngenic bone marrow tran splantation. Interestingly, these gamma delta T cells express mainly t he V(gamma)3 TCR, which is characteristic of dendritic epithelial T ce lls that can develop in athymic nude mice and may recognize self antig ens. Since the peripheral expansion of V(gamma)3 T lymphocytes is clos ely related to bone marrow age, these observations indicate that the a ge-related propensity to extrathymic development of V(gamma)3(+) gamma delta(+) T lymphocytes is mainly due to stem cell dysregulation in ag ing. This phenomenon may contribute to T cell impairment and to the in creased natural cytotoxic activity of lymphoid cells in aged mice.