Critical role of the CD44lowCD62Llow CD8+ T cell subset in restoring antitumor immunity in aged mice.

Abstract

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.

• Authors: Yuka Nakajima, Kenji Chamoto, Takuma Oura, Tasuku Honjo
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 118 Issue 23 (06 08 2021) ISSN: 1091-6490 [Electronic] United States
• PMID: 34088845 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Cd44 protein, mouse
• Hyaluronan Receptors
• Pdcd1 protein, mouse
• Programmed Cell Death 1 Receptor
• L-Selectin

Topics

• Aging (genetics, immunology)
• Animals
• CD8-Positive T-Lymphocytes (immunology)
• Cell Line, Tumor
• Hyaluronan Receptors (genetics, immunology)
• L-Selectin (genetics, immunology)
• Mice
• Mice, Knockout
• Neoplasms, Experimental (genetics, immunology)
• Programmed Cell Death 1 Receptor (deficiency, immunology)