The relationship of cytomegalovirus (CMV) infection with circulatory IFN-α levels and IL-7 receptor α expression on CD8+ T cells in human aging

The IL-7 receptor alpha (IL-7R alpha) is the high affinity receptor for IL-7 which is essential for T cell homeostasis. We recently reported an age-associated expansion of human effector memory (EM) CD8(+) T cells expressing IL-7R alpha low (IL-7Ra alpha(low)), which could be detrimental to hosts by occupying immunological space. We investigated the potential mechanisms for this phenomenon, focusing on cytomegalovirus (CMV) infection and INF-alpha. In the elderly (age >= 65), CMV infection was associated with a decreased frequency of naive CD8(+) T cells as well as with an increased frequency of total EM and IL-7R alpha(low) EM CD8(+) T cells. However, in the young (age <= 40), this viral infection was associated only with an increased frequency of IL-7R alpha(low) EM CD8(+) T cells. There was no association found between CMV immune status and plasma levels of IFN-alpha. In CMV-infected young and elderly people, INF-alpha levels had no correlation with the frequency of IL-7R alpha(low) EM CD8(+) T cells although this cytokine levels correlated with the frequency of IL-7R alpha(low) CD45RA(+) EM CD8(+) T cells in CMV-uninfected elderly people. Our findings suggest that the effect of CMV infection on the frequency of CD8(+) T cell subsets may begin with IL-7R alpha(low) EM CD8(+) T cells and spread to other subsets with aging. Also, IFN-alpha could be associated with the expansion of IL-7R alpha(low) CD45RA(+) EM CD8(+) T cells in the CMV-uninfected elderly. (C) 2012 Elsevier Ltd. All rights reserved.