Immune Checkpoint Function of CD85j in CD8 T Cell Differentiation and Aging

Area of Science:

• Immunology
• Aging research
• T cell biology

Background:

• Aging impairs immune function, increasing infection susceptibility and altering CD8 T cell responses.
• The aging T cell repertoire shows increased effector CD8 T cells expressing the CD85j receptor.
• The role of CD85j in immune aging and its impact on CD8 T cell function require clarification.

Purpose of the Study:

• To investigate the biological significance of CD85j expression on CD8 T cells in aging.
• To determine if CD85j is beneficial or detrimental to immune function in older individuals.
• To analyze the role of CD85j in antigen-specific CD8 T cell responses during immune aging.

Main Methods:

• Examined CD85j expression on CD8 T cells in aging populations, particularly in cytomegalovirus (CMV) infection.
• Performed phenotypic and functional analyses of CD85j+ CD8 T cells, including senescence markers and cytokine production.
• Investigated the effect of blocking CD85j binding on CMV-specific CD8 T cell proliferation and function.

Main Results:

• CD85j is primarily expressed on terminally differentiated effector memory CD8 T cells (TEMRAs) that increase with age, CMV infection, and in males.
• CD85j+ CMV-specific CD8 T cells show clonal expansion but similar TCR diversity to CD85j- cells.
• CD85j identifies senescent, polyfunctional CD8 T cells that retain cytotoxic mediator expression; blocking CD85j enhances proliferation but not cytokine production.

Conclusions:

• CD85j identifies a distinct population of senescent, but not exhausted, antigen-specific effector CD8 T cells.
• CD85j acts as a checkpoint regulator controlling the expansion of virus-specific T cells during aging.
• Inhibiting CD85j activity presents a potential strategy to enhance CD8 T cell effector responses in immune aging.