Functional CD8 T cell memory responding to persistent latent infection is maintained for life

A Lang, J Nikolich-Žugich - The Journal of Immunology, 2011 - journals.aai.org
The Journal of Immunology, 2011journals.aai.org
Aging is associated with depressed naive T cell responses, but it is less clear whether T cell
memory established early in life also becomes impaired with age. This is particularly
important for T cells responding to latent persistent infection, which need to remain
functional and capable of controlling the infection over the lifetime; however, repeated
stimulation over the lifetime may dysregulate their maintenance or function, potentially
contributing to impaired immunity in the elderly. Systemic infection with HSV-1, a persistent …
Abstract
Aging is associated with depressed naive T cell responses, but it is less clear whether T cell memory established early in life also becomes impaired with age. This is particularly important for T cells responding to latent persistent infection, which need to remain functional and capable of controlling the infection over the lifetime; however, repeated stimulation over the lifetime may dysregulate their maintenance or function, potentially contributing to impaired immunity in the elderly. Systemic infection with HSV-1, a persistent latent virus, is associated with memory inflation of virus-specific CD8 T cells. We tested how these inflated memory cells are maintained from adulthood into old age. We found no significant differences in the numbers (ie, blood, spleen), ex vivo Ag-specific IFN-γ production, and in vivo recall response to HSV-1 (ie, proliferation, IFN-γ production, cytolysis) between adult and old memory T cells. There was a discrete shift from dominantly effector memory phenotype in the adults to a central memory-like phenotype in the old mice, with fewer old cells expressing the killer cell lectin-like receptor G1 (KLRG1). Adult and old KLRG1+ memory CD8 T cells were functionally identical: both produced IFN-γ but could minimally proliferate in response to viral challenge. Interestingly, regardless of age, KLRG1+ cells retained the ability to proliferate and survive in response to homeostatic signals, both in vitro (culture with IL-7 and IL-15) and in vivo (expansion following transfer into lymphopenic recipients). This finding demonstrates that functional effector memory T cells, including those expressing KLRG-1, are maintained and are functional for life, despite the presence of persistent viral infection.
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