Decreased membrane potential of T lymphocytes in ageing mice: flow cytometric studies with a carbocyanine dye.

The membrane potential of lymphocytes from young (1-4-month-old) and old (25-37-month-old) CBA/Ca mice was studied with the aid of the fluorescent dye 3,3'-dihexyloxacarbocyanine iodide (DiOC6(3)). In young mice, most B and T lymphocytes showed a high, and equal, degree of polarization. In old animals most, and in the older individuals almost all, T lymphocytes were found to be depolarized; both Lyt-2+ and Lyt-2- subsets were affected. B cells were largely unaffected. Since changes in transmembrane potential, including temporary hyperpolarization, are known to accompany lymphocyte activation, the depolarized state of T cells in old mice may be related to the decline of T-cell function that occurs during senescence.