Aging reshapes the immune system in two fundamental ways: it alters the proportions of different immune cell types circulating in the blood, and it induces molecular changes within each individual cell. For years, researchers have struggled to disentangle these two intertwined processes using standard “bulk” measurements, which average signals across millions of cells and obscure what is happening at the single-cell level.

A new research paper, titled “Single-cell transcriptomics reveal intrinsic and systemic T cell aging in COVID-19 and HIV” published in Volume 18 of Aging-US by researchers at the Buck Institute for Research on Aging in California, the University of Southern California, and the University of Copenhagen, introduces an innovative solution.

The team of Alan Tomusiak, Sierra Lore, Morten Scheibye-Knudsen, and corresponding author Eric Verdin, developed a novel tool called Tictock (T immune cell transcriptomic clock) that uses single-cell RNA sequencing to separately measure systemic and cell-intrinsic components of immune aging, and then applied it to understand how COVID-19 and HIV affect T cells.

Full blog - https://aging-us.org/2026/03/tictock-a-single-cell-clock-measures-immune-aging-in-viral-infections/

Paper DOI - https://doi.org/10.18632/aging.206353

Corresponding author - Eric Verdin - [email protected]

Abstract video - https://www.youtube.com/watch?v=_r3AF7OrgKY

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Keywords - aging, transcriptomic clock, aging biomarkers, systemic aging, intrinsic aging

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