Researchers at the Max Planck Institute for Physics and Medicine in Erlangen, Germany, have demonstrated that COVID-19 significantly alters the size and rigidity of red and white blood cells for periods sometimes extending over months. They utilized an innovative method called "real-time deformability cytometry" (RT-DC). New evidence suggests that the lasting imprint of COVID-19 may be due to the virus's impact on people's blood, leading to permanent changes in blood cells that remain evident months after the infection is diagnosed.
Biophysicist Jochen Guck from the Max Planck Institute for the Science of Light explains, "We were able to detect clear and enduring changes in the cells—during the acute infection and even afterward." In a new study, Guck and his fellow researchers analyzed blood samples from patients using an internally developed system called real-time deformability cytometry (RT-DC), capable of rapidly analyzing hundreds of blood cells per second and detecting any abnormal changes in their size and structure.
These findings help explain why some individuals infected with COVID-19 continue to report symptoms long after their initial infection. Some patients suffer from long-term effects of severe viral infection, experiencing symptoms such as shortness of breath, fatigue, and headaches for six months or more after recovery. This condition, known as "post-COVID-19 syndrome," remains poorly understood.
What is clear is that during the course of the illness, the circulatory system often becomes disrupted, with serious blockages occurring in blood vessels, limiting oxygen transport—phenomena in which blood cells and their physical properties play a crucial role. The research team measured the mechanical state of red and white blood cells to investigate this aspect and identified clear and long-lasting changes in the cells, both during acute infection and afterward. They published their findings in the Biophysical Journal.
Using their self-developed method, recognized with the prestigious "Medical Valley" award, researchers analyzed blood cells. In this method, researchers send blood cells through a narrow channel at high speed, stretching white and red blood cells in the process. A high-speed camera captures each cell through a microscope, and a dedicated program identifies cell types and measures their size and deformation, allowing analysis of up to 1,000 blood cells per second.
This relatively new technology could greatly contribute to exploring what remains unknown about COVID-19: how the coronavirus can affect blood at a cellular level. This method may also serve as an early warning system for detecting future pandemics caused by unknown viruses.
The scientists examined more than 4 million blood cells from 17 severely ill COVID-19 patients, 14 recovered individuals, and 24 healthy individuals as a control group. They found that the size and deformation of the red blood cells in patients with this disease significantly deviated from those of healthy individuals, indicating damage to these cells and potentially explaining the increased risk of vascular blockages and obstruction in the lungs. Additionally, the oxygen supply, a primary task of red blood cells, may be affected in infected persons.
Lymphocytes (a type of white blood cell responsible for acquired immune defense) were notably softer in COVID-19 patients, typically indicating a strong immune response. The researchers also observed similar findings in neutrophils, another group of white blood cells involved in the innate immune response, with these cells remaining drastically altered even seven months after the acute infection.
