Long COVID: How Altered Immune Cells Cause Lasting Fatigue & Breathlessness

For many, recovery from a COVID-19 infection isn’t a clear return to health. Even after testing negative, lingering effects can include persistent fatigue, difficulty with physical exertion, and shortness of breath. This condition, known as Long COVID, is increasingly recognized as more than a marginal issue. Estimates suggest that up to one in ten people in Germany experience ongoing symptoms after infection.

Immunzellen liefern Hinweise auf die Ursache von Long COVID

Interestingly, Long COVID often affects individuals who experienced mild initial infections – those who did not require hospitalization, oxygen support, or even develop a fever. Despite this, symptoms like profound exhaustion, breathing difficulties, and trouble concentrating can persist for months. A recent large-scale immunological analysis offers a potential explanation for this puzzling phenomenon.

The research highlights the role of CD14⁺-Monozyten, specialized white blood cells that normally respond to inflammation and help control infections. In many individuals with Long COVID, these cells behave unexpectedly. Specifically, the study identified a distinct internal state within these Monozyten, characterized by altered gene activity, internally referred to as “LC-Mo.” This state is particularly prevalent in those who initially had mild or moderate COVID-19 infections, and who subsequently developed Long COVID.

Entzündungsstoffe halten den Körper in Alarmbereitschaft

Accompanying this cellular change, blood tests of many affected individuals reveal elevated levels of inflammatory markers, including TNF, CCL2, and CXCL11. These substances signal danger to the immune system, but remain active even after the virus has cleared. The body struggles to return to a normal resting state.

This persistent state of alert isn’t merely a laboratory finding; it has tangible consequences. The more pronounced the altered Monozyten state, the more severe the fatigue often becomes. Breathing problems are also more frequent, sometimes accompanied by slightly reduced blood oxygen levels – enough to make physical activity significantly more challenging.

Immunzellen verändern das Lungengewebe spürbar

Further analysis of samples from the airways revealed the presence of immune cells with similar characteristics. These cells carry genes associated with tissue remodeling processes, known as profibrotic programs. This suggests that lung tissue may lose elasticity, aligning with the shortness of breath reported by many patients, even with minimal exertion.

The symptoms, appear less random. Exhaustion and breathing difficulties can be linked to interconnected processes within the immune system that reinforce each other.

Ein biologischer Zwischenzustand mit Folgen

Typically, the immune system responds flexibly, ramping up to fight off pathogens and then returning to a resting state. In Long COVID, this mechanism appears disrupted. In laboratory tests, Monozyten exhibiting the “LC-Mo” state showed a diminished response to new stimuli. Their interferon response, a crucial part of antiviral defence, was suppressed, and other immune signals were also reduced.

This combination of inflammation and immune system sluggishness may explain why symptoms become entrenched, trapping the body in an intermediate state. Long COVID, exhibits a distinct biological profile compared to classic fatigue syndromes.

Langzeitdaten machen Veränderungen im Blut sichtbar

The analysis, based on data collected over months from multiple patient groups, revealed a temporal pattern. The altered Monozyten state often became more pronounced around three months post-infection and persisted for nearly a year in some cases. Key observations from the data include:

• The specific cell state is most common after mild COVID-19 infections.
• Higher proportions of these Monozyten correlate with increased fatigue.
• Breathing problems are linked to elevated inflammation and altered immune cells.

These connections don’t explain every individual case, but they provide a framework for understanding the relationship between symptoms and laboratory findings.

Zusammenhänge werden greifbarer

The analysis involved collaboration between several research institutions, including the Helmholtz-Zentrum für Infektionsforschung. The findings were published in the journal Nature Immunology. Study leader Yang Li describes Long COVID as an “extremely complex disease with various manifestations,” emphasizing that the identified cell state is another piece of the puzzle, not a definitive explanation.

Researchers emphasize that the results demonstrate correlations, but do not prove a direct cause-and-effect relationship. However, they do allow for the measurement and comparison of concrete biological processes.

Neue Ansatzpunkte für Diagnose und Therapie

This understanding offers validation for many experiencing Long COVID, providing a tangible basis for their symptoms. It also opens new avenues for potential therapies, such as approaches to dampen inflammatory signals or modulate the function of these altered immune cells. Key takeaways include:

• The root of Long COVID doesn’t necessarily lie in severe acute illness.
• Changes in the immune system can persist long after the initial infection.

Kurz zusammengefasst:

• Long COVID is often linked to a persistent altered state of specific immune cells, maintaining inflammation even after mild infections.
• This altered cell state correlates with elevated inflammation and is associated with fatigue and breathing problems.
• These findings explain the prolonged nature of symptoms and provide a measurable biological basis for Long COVID.

Übrigens: Persistent exhaustion, concentration problems, or sleep disturbances after COVID-19 can resemble Long COVID – but may also indicate an untreated depression. A large German study warns against misdiagnosis and missed opportunities for help. More information is available in our article.

Frequently Asked Questions

What type of immune cells are particularly affected in Long COVID?

CD14⁺-Monozyten, specialized white blood cells, play a key role. These cells exhibit an altered state, referred to as “LC-Mo,” in many individuals with Long COVID.

Are elevated inflammation levels consistently found in Long COVID patients?

Yes, blood tests of many affected individuals reveal increased levels of inflammatory markers like TNF, CCL2, and CXCL11, even after the virus has been cleared.

How long after the initial infection does this altered immune cell state typically become noticeable?

The altered Monozyten state often becomes more pronounced around three months after the initial infection and can persist for up to a year in some cases.