Evidence for a less differentiated subpopulation of lymphocytes in people of advanced age

The ratio of the lactate dehydrogenase subunits, H/M, is shifted toward lower values in thymocytes, and in high-density T cells in normal peripheral blood. The results presented here indicate that the T cells, but not B cells or monocytes, of donors greater than 75 years' old have a significantly reduced H/M ratio relative to young adults. This reduced H/M ratio appears to be correlated with a diminished percentage of OKT3 positive cells in the old donors. However, the density distribution of cells from young and old on Percoll gradients indicates that the T cells with lower H/M ratio in the elderly may represent a distinct, and possibly unique, less differentiated T cell type.