Ratio of two immune cell types tracks healthy versus unhealthy ageing, Immunity study finds

A study published on 9 October in Immunity, led by Washington University School of Medicine in St. Louis, Nationwide Children’s Hospital and King’s College London, maps how the human immune system ages — and why two people of the same age can age very differently.

What they did

• Analysed about 12.4 million immune cells from the blood of 2,609 mostly healthy adults aged 20 to 90-plus in eight cohorts across North America, the UK, Asia and Australia.
• Focused on memory T cells that make either granzyme K (GZMK) or granzyme B (GZMB).
• Identified a blood-protein signature of GZMB-dominant immunity in 329 people and then looked for it in roughly 48,000 UK Biobank participants with long-term health records.

Findings

Healthy ageing was associated with a shift toward GZMK cells. People whose immune profile leaned toward GZMB cells had a higher risk of death about a decade later and were more likely to develop type 2 diabetes, hypertension, liver disease and kidney failure, the authors report.

Limitations

The study shows an association; a study author quoted by Live Science stressed it does not prove the ratio causes poor health. The UK Biobank part relied on a protein proxy for the cell ratio, not direct cell counts, and UK Biobank volunteers are healthier than the general population. No test or treatment based on the ratio is available yet.