A marker that triggers T cells to fight an infection in the gut was found in small numbers in those with a SARS-CoV-2 infection.
A recent study conducted by investigators from the University Hospital Erlangen in Germany has found that our gut’s immune response to COVID-19 may not provide long-lasting systemic immunity in comparison to the immune response triggered elsewhere in the body.
Results from the study were published in the journal Frontiers in Immunology.
"Although the gut is considered an important portal of entry for the virus, the immune response in the blood of COVID-19 patients is dominated by lymphocytes - cells that protect the body from infection - that have been triggered by other areas of the body," Sebastian Zundler, an author on the study said. “Further work is needed, but these findings may have implications for oral COVID-19 vaccines.”
For the study, the investigators employed a technique that detects and measures differing immune cells that are found in the blood, called flow cytometry. They used this to analyze blood samples from people who were currently infected with COVID-19, those who had recovered from the disease, and those who did not have the virus.
"There is a special mechanism in the lymphoid tissue of the gut that triggers the production of an imprint marker called ‘a4b7 integrin’,” Tanja Müller, lead author on the study said. “This marker causes T cells to head towards the gut to fight infection. We can use this marker to identify whether there are lymphocytes circulating in the blood that were triggered by the gut's immune response.”
The investigators found relatively few immune cells that had the a4b7 markers in the blood of those patients with a COVID-19 infection. The authors speculated that this could be because dilution caused by cells that were created at other sites of infection.
"Our study adds to our understanding of the human immune response to SARS-CoV-2 infection, but we cannot yet finally answer the question about the fate of the gut-imprinted immune cells - whether they are "diluted" or "attracted" elsewhere,” Zundler said. “Assessing biopsy samples from the gut and autopsy samples from the lungs will help us to answer this important question."