Mouse liver T cells: Their change with aging and in comparison with peripheral T cells

Mouse liver contains both IL-2R beta(-)(or low positive) high T-cell receptor (TCRhi) cells and IL-2R beta(+) intermediate TCR (TCRint) cells, TCRint cells consist of natural killer 1.1 (NK1)(+) and NK1(-) subsets. NK1(-)TCR(int) cells increase constantly with age whereas TCRhi cells decrease, NK1(+) TCRint cell proportions in the liver increase until middle age and decrease thereafter. Although NK1(+) TCRint cells in other organs are few regardless of age, NK1(-) TCRint cells gradually appear in other lymphoid organs with aging. Skewed usage of V beta 7 and V beta 8 TCR was observed in NK1(+) TCRint cells in the liver but the predominance was less obvious in NK1(-) TCRint and TCRhi cells in the liver and other organs. TCR V alpha 14 messenger RNA (mRNA) was detected in NK1(+) TCRint cells but not in the other two populations, In contrast, although NK1(+) TCRint cells contain virtually no V alpha 11(+) T cells, NK1(-) TCRint cells contain a much higher proportion (approximately 12%) of V alpha 11(+) T cells, whereas approximately 4% of TCR cells are V alpha 11(+). NK activities of liver mononuclear cells (MNC) and splenocytes decrease with aging, although the former is always greater than the latter. NK activity of liver MNC is a function of NK cells, partly NK1(+) TCRint cells but not NK1(-) TCRint cells or TCRhi cells. These results suggest that lymphocytes of liver and other organs at old age are no longer occupied solely by conventional thymus-derived T cells, and the increase of extrathymic IL-2R beta(+) NK1(-) TCRint cells in liver and periphery could be closely related to immunological changes with aging.