Valpha24+ NKT cells are decreased in elderly humans.

Natural killer T (NKT) cells represent a novel cell lineage characterized by the restricted expression of an invariant TCRalpha chain encoded by Valpha24/JalphaQ gene segments in humans and Valpha14/Jalpha281+ in mice. Different aspects of the immune response are severely affected by age. Thus, we have studied the effect of aging on NKT cells from healthy elderly individuals. Our results demonstrated a decreased percentage of CD3+Valpha24+ cells in peripheral blood from elderly donors, whereas mainstream T lymphocytes showed an age-associated decrease in the expression of CD28, the vast majority of CD3+Valpha24+ cells from old individuals were CD28+. A significant increase in the percentage of Valpha24+ cells with the CD4-CD8+ phenotype was also found in the elderly, indicating a redistribution of Valpha24+ subsets according to the CD4/CD8 phenotype. Given the important immunoregulatory role of these cells, the decrease of NKT cells will contribute to the deleterious immune response in the elderly.