Study Validates That COVID-19 Reduces Not Just Killer T-Cells (CD8) But Also Helper T-Cells (CD4) That Worsens with Age
Nikhil Prasad Fact checked by:Thailand Medical News Team Sep 26, 2025 3 months, 3 weeks, 5 days, 5 hours, 27 minutes ago
Medical News: Understanding the Immune System Damage
A new study by researchers from the Department of Orthopedics at the Cancer Hospital of Shantou University Medical College and the Department of Clinical Laboratory Medicine and Division of Hematology at the Second Affiliated Hospital of Shantou University Medical College, Guangdong, China, has revealed how COVID-19 severely damages the immune system by reducing T-lymphocytes, the white blood cells that play a key role in defending the body.
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Study Validates That COVID-19 Reduces Not Just Killer T-Cells (CD8) But Also Helper T-Cells (CD4) That Worsens with Age
The research team studied 60 COVID-19 patients of different ages and disease severity and compared them with 36 healthy individuals. By analyzing blood samples with advanced flow cytometry, they found that COVID-19 patients had significantly fewer T-lymphocytes and imbalances in their subpopulations. This
Medical News report highlights how the loss of these immune cells is worse in elderly and critically ill patients, suggesting that age and disease severity make the body more vulnerable.
Key findings from the study
The study revealed that both helper T cells (CD4+) and killer T cells (CD8+) were sharply reduced in COVID-19 patients. These cells normally work together to fight infections—helper T cells coordinating immune responses and killer T cells directly destroying virus-infected cells. However, in severe and critical COVID-19 patients, these cells were drastically lower than in those with mild illness.
Importantly, the researchers observed that naïve CD8+ T cells, which are responsible for responding to new infections, were negatively linked with age. Older patients had significantly fewer of these cells, meaning their ability to mount fresh defenses against SARS-CoV-2 was weaker. Memory T cells, which recall past infections, were relatively higher, but the overall immune system balance was disrupted.
Another major finding was that regulatory T cells (Tregs), which normally prevent excessive immune reactions, appeared elevated in relative terms, potentially dampening the body’s fight against the virus. Yet in critically ill patients, the absolute numbers of these protective cells dropped, further destabilizing immune defenses.
Implications for severe and elderly patients
The results underline that SARS-CoV-2 attacks the body not only by infecting tissues but also by crippling immune coordination. For older patients, the natural decline of the thymus gland, which produces T cells, combined with the impact of the virus, may explain why they are more likely to develop severe or fatal outcomes. By monitoring the different T-cell types and their proportions, doctors may better predict which patients are at higher risk and intervene earlier with tailored treatments.
Why this matters for future care
This research confirms that COVID-19 is not just a respiratory illness but also a disease that severely weakens cellular immunity. As the world continues to face new variants, understanding
these immune changes is crucial for developing therapies and improving patient survival. The findings strongly suggest that in-depth tracking of T cell health could guide doctors in managing COVID-19 and possibly other viral infections.
The study findings were published in the peer reviewed journal: Biochemistry Research International.
https://onlinelibrary.wiley.com/doi/10.1155/bri/5791950
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https://www.thailandmedical.news/news/long-covid-linked-to-the-altered-functionality-of-cd4-t-helper-th-cells
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