The researchers have said that lots of people who lost their smell after they contracted coronavirus may be facing abnormal immune responses in which they suffer nasal cell destruction.
The nasal tissue of Covid patients was analysed by doctors who found inflammation-driving immune cells present inside the delicate nasal lining of those people who were facing the loss of smell which was probably removing vital sensory nerve cells.
North Carolina Duke University neurobiology department’s associate professor Dr Bradley Goldstein said that tissues present inside the nose lining “contained unique immune cells producing inflammatory signals, combined with fewer olfactory nerve cells”.
The research found unusual immune responses present in patients who are suffering from the loss of sense of smell for months. “It appears that there is an unresolved local immune response, which the delicate olfactory cells are seeing,” he said.
Since it was brought to the notice of doctors that many Covid patients are suffering the loss of smell, it has remained unclear if the sensory cells present in the nose and around the brain have individually or together suffered damage by the virus.
Biopsied tissue present in 24 Covid patients’ nasal linings was studied by the researchers, which included nine patients who had no sense of smell for at least four months.
In the tissue, it was found that the nasal lining was infiltrated by T-cells involved in inflammation where smell nerve cells are present.
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This unusual immune response was present in patients who had no detectable coronavirus, which further indicated that the response persisted after the clearance of infection.
When the number of sensory nerve cells which are involved in smell was studied by the researchers, it was found that those suffering from loss of smell for a long time had fewer cells because the nasal lining’s delicate issue was damaged by the T-cell-driven inflammation.
Goldstein added that other symptoms of Covid might be explained by similar immune responses.
“Currently, we have no specific, effective treatments. To develop therapies, we need to understand the pathobiology of the problem: what is damaged and where,” he added.
(With inputs from agencies)
