Researchers at the La Jolla Institute (LJI) in the United States have found that immune memory cells that get developed from exposure to common cold viruses can also discern SARS-CoV-2, as per a Live Science report.

The study said this is the reason why there are different levels of Covid-19 severity found in people — their immune responses are different from one another. Their findings were published on Tuesday.

Corroborating the analysis made by the scientists in Germany, the US researchers maintained that memory helper T cells recognise matching molecular structural sites on SARS-CoV-2. The T-cells are a part of the multi-armed immune system that protects the body from harmful microbial agents.

“This could help explain why some people show milder symptoms of the disease while others get severely sick,” Daniela Weiskopf, an assistant professor at the LJI, said in a media release.

“Immune reactivity might translate into different degrees of protection. Having a stronger T cell response or a better T cell response might give you the opportunity to mount a much quicker and stronger response.”

However, researchers also noted that there is no substantial proof that T-cells are associated with the severity level of the disease.

Spike protein recognition

According to the German study, 24 (35 per cent) of 68 healthy individuals, who were unexposed to SARS-CoV-2 had T-cells that were capable of recognising spike proteins of coronavirus that match with harmless common cold coronaviruses.

“If we assume these cold viruses are capable of conferring a certain level of immunity against SARS-CoV-2, this would mean people who have had frequent exposure to such infections in the past and who test positive for the cross-reactive T cells should have better protection,” said Andreas Thiel, a senior researcher at Charité – Universitätsmedizin Berlin, who supervised the study as cited in the Telegraph report.

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