Age-related changes in the degeneracy of the mouse T-cell repertoire

Aging is associated with a decline in T-cell-dependent immune responses. As the number of T-cells remains relatively constant throughout life, the observed decline in T-cell function may reflect qualitative changes in the T-cells themselves or in the composition of the T-cell population. In this investigation, the quality of the T-cell response was studied in young-adult and aged B6C3F1 mice by assessing the degeneracy of the hapten-specific proliferative response to the antigen-MHC complex. Degeneracy was defined as the ability of lymph node cells from mice contact-sensitized to the hapten TNP to proliferate in response to in vitro stimulation with haptenated allogeneic antigen-presenting cells, thus escaping strict MHC restriction. It was found that, although degeneracy occurred in both age groups, it was more prevalent and of a greater magnitude in the young than in the old lymphocytes. These results suggest that there are qualitative differences in T-cell populations derived from young-adult and aged mice.