Omicron cannot escape body’s second-line defense

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A key part of the immune system’s second-line defense – its T cells – are highly effective at recognizing and attacking the Omicron variant, thereby preventing most infections from progressing to critical illness, a new study shows.

Omicron’s mutations help it escape from antibodies, the body’s first line of defense against infection. Researchers have speculated that other components of the immune response would still target Omicron, but there has been no proof until now.

In test tube experiments, researchers in South Africa exposed copies of the virus to T cells from volunteers who had received vaccines from Johnson & Johnson or Pfizer/BioNTech or who had not been vaccinated but had developed their own T cells after infection with an earlier version of the coronavirus.

“Despite Omicron’s extensive mutations and reduced susceptibility to neutralizing antibodies, the majority of T cell response, induced by vaccination or natural infection, cross-recognizes the variant,” the researchers reported on this week on medRxiv ahead of peer review.

“Well-preserved T cell immunity to Omicron is likely to contribute to protection from severe COVID-19,” which supports what South African doctors had initially suspected when most patients with Omicron infections did not become seriously ill, they said.

The “T” stands for thymus, the organ in which the cells’ final stage of development occurs.

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