Researchers studying mice flown aboard the International Space Station found higher numbers of several lung immune-cell populations after exposure to an artificial-gravity environment equivalent to one-sixth of Earth’s gravity. The Japan Aerospace Exploration Agency announced the published findings on November 13, 2026.
The study examined lung tissue from animals housed in Japan’s Kibo laboratory. It measured CD8-positive T cells and a subset known as tissue-resident memory T cells. CD8-positive cells participate in responses against infected or abnormal cells, and tissue-resident memory cells remain in organs where they contribute to local immune memory.
Counting Cells in Preserved Tissue
Erika Osada, Hiroki Bochimoto, and Yohei Sato authored the Life Sciences in Space Research paper. Its findings concern immune-cell populations in mice following spaceflight under partial gravity.
The researchers used flow cytometry, a method that passes cells through an instrument to identify and count populations according to their measured properties. Applying the technique to lung tissue requires separating cells from the tissue before measurement.
The published abstract describes an optimized enzyme-based method for processing frozen lung samples. The researchers performed the measurements without a magnetic-enrichment step for CD45-positive cells, seeking to preserve viable cells and their surface markers.
After statistical adjustment for multiple comparisons, absolute counts of CD8-positive T cells, CD69-positive CD8 T cells, and CD8-positive tissue-resident memory T cells were higher in the spaceflight group than in ground controls. The corresponding proportions did not show statistically significant differences after that adjustment.
Absolute counts and proportions describe different features of a sample. A population can contain more cells without making up a larger share of all the cells measured. The authors described an association with higher cell numbers rather than selective expansion of the tissue-resident memory compartment.
The experiment used ground controls without a simultaneous artificial one-gravity control aboard the station. Its comparison concerns the combined spaceflight and partial-gravity conditions; it does not isolate gravity as the cause of the observed differences.
Research From Shared Spaceflight Samples
The work used JAXA’s mouse biospecimen-sharing program. That program supplies previously collected tissue to selected researchers, allowing additional studies after an orbital animal mission has ended.
Researchers can examine organs and tissues for questions beyond those addressed by the original flight investigation. The available specimens retain the housing and flight conditions of their source mission, making those conditions part of the design of each later analysis.
JAXA operates the sharing effort through domestic research selections and international collaboration, including work with NASA and Asian space agencies. Its repository also distributes eligible unused tissues to researchers in Japan and the United States.
The lung study adds a tissue-specific result to that shared research record. The reported measurement is an increase in selected immune-cell counts in preserved mouse lung tissue following the station experiment.
