Critical role of the CD44lowCD62Llow CD8+ T cell subset in restoring antitumor immunity in aged mice.
Yuka NakajimaKenji ChamotoTakuma OuraTasuku HonjoPublished in: Proceedings of the National Academy of Sciences of the United States of America (2021)
CD8+ T cells play a central role in antitumor immune responses that kill cancer cells directly. In aged individuals, CD8+ T cell immunity is strongly suppressed, which is associated with cancer and other age-related diseases. The mechanism underlying this age-related decrease in immune function remains largely unknown. This study investigated the role of T cell function in age-related unresponsiveness to PD-1 blockade cancer therapy. We found inefficient generation of CD44lowCD62Llow CD8+ T cell subset (P4) in draining lymph nodes of tumor-bearing aged mice. In vitro stimulation of naive CD8+ T cells first generated P4 cells, followed by effector/memory T cells. The P4 cells contained a unique set of genes related to enzymes involved in one-carbon (1C) metabolism, which is critical to antigen-specific T cell activation and mitochondrial function. Consistent with this finding, 1C-metabolism-related gene expression and mitochondrial respiration were down-regulated in aged CD8+ T cells compared with young CD8+ T cells. In aged OVA-specific T cell receptor (TCR) transgenic mice, ZAP-70 was not activated, even after inoculation with OVA-expressing tumor cells. The attenuation of TCR signaling appeared to be due to elevated expression of CD45RB phosphatase in aged CD8+ T cells. Surprisingly, strong stimulation by nonself cell injection into aged PD-1-deficient mice restored normal levels of CD45RB and ameliorated the emergence of P4 cells and 1C metabolic enzyme expression in CD8+ T cells, and antitumor activity. These findings indicate that impaired induction of the P4 subset may be responsible for the age-related resistance to PD-1 blockade, which can be rescued by strong TCR stimulation.
Keyphrases
- induced apoptosis
- gene expression
- cell cycle arrest
- regulatory t cells
- immune response
- lymph node
- cancer therapy
- poor prognosis
- oxidative stress
- dendritic cells
- cell death
- early stage
- single cell
- hiv infected
- mesenchymal stem cells
- working memory
- young adults
- squamous cell carcinoma
- cell proliferation
- high fat diet induced
- pi k akt
- toll like receptor
- high resolution
- wild type