Platelets are not only involved in blood coagulation and the development of thrombosis. Researchers from Utrecht University, UMC Utrecht and Erasmus MC have now discovered that they also play a role in our immune system: they appear to be indispensable in protecting our respiratory system against pathogens. "In patients with flu, the platelets absorb virus particles from the lungs, after which they return to the bloodstream”, says lead researcher Erhard van der Vries. This insight is also important for research into coagulation and acute cardiovascular problems in corona patients, such as strokes and blood clots in the pulmonary vessels.

That there is a relationship between respiratory tract infections and acute cardiovascular events was already known. For example, the weekly mortality rate, linked to cardiovascular events, shows a seasonal pattern, which coincides with the annual flu season. Conversely, elderly people who get the flu shot are 20 percent less likely to end up in hospital because of cardiovascular events or a stroke. The researchers expect to see the same relationship in corona patients. The double function of blood platelets –  in blood coagulation and in the immune system – may play a key role in this.

Van der Vries (molecular virologist at GD Deventer, UMC Utrecht and Utrecht University): "We know from international research that the flu shot greatly reduces the risk of acute cardiovascular diseases, such as strokes. The mechanism behind this was hitherto unknown. This research shows that an early immune response of platelets plays an important role during the flu. However, the same immune response can also lead to complications in certain situations. This seems to be the case, for example, in coronary patients, where the immune response can also lead to a pulmonary embolism, causing patients to end up in the ICU. We now want to investigate this further in animals and humans with a multidisciplinary team of virologists, haematologists and immunologists.”

Blood tests

The role of platelets in the immune system requires further investigation. An important question that the researchers still hope to answer is when platelets end up in the lungs during the flu, where they then go and how they share their collected virological information with other immune cells. Hospitals can also specifically look at the relationship between respiratory tract infections and platelet information from blood tests. This data may possibly help in the diagnosis of pneumonia.

The findings of this research may also contribute to the development of new therapies for acute cardiovascular problems and the prediction of complications in respiratory tract infections. In the long term, they may also help in the development of better vaccination strategies.

Publication

Jansen AJG, Spaan T, Low HZ, Di Lorio D, Brand J van den, Tieke M, et al. Influenza-induced thrombocytopenia is subtype and sialoglycan receptor dependent and increases with virus pathogenicity - Platelets mediate influenza clearance external link. Blood Advances 2020;4(13):2967–2978