Published: 04 Feb 2022, 01:44 pm
The rapid spread of Omicron across the world at a time when the world has already seen two waves of the pandemic has revealed several surprising things about the human immunity system. The immunity system remembers past infection but for SARS-CoV-2, it has not been very long, reports Hindustan Times.
A study published in Nature has taken a deep dive into this and outlined how the immune system against Covid and its variants work.
Here are the 10 points about human immunity:
1. B cells are the first responders and when a pathogen attacks, they get activated. B cells churn out antibodies and then they die.
2. It was not surprising to scientists that neutralising antibody levels were dropping after a few months because antibodies are supposed to wane.
3. There are short-live B cells and long-lived B cells. While short-lived B cells die, some long-lived B cells become memory B cells which can rapidly divide and become plasma cells when encountered by a virus. These cells live with us for the rest of our lives.
4. This response of the memory B cell improves over time. In a study, it was found that six months after vaccination, individuals had an elevated number of memory B cells that also responded to new variants.
5. Another pillar of immune memory are T cells. They kill the virus and also send signals to other parts of the immune system to get activated against the virus attack. Some T cells then become memory T cells.
7. Some people might carry memory T cells from past coronavirus infections — such as those that cause common colds — that can recognise SARS-CoV-2.
8. According to the observation of immunologists, memory cells typically can't block infection in the way that neutralising antibodies can, but they don't necessarily need to.
9. After the Covid-19 infection, the memory cells get some time as serious illness generally does not take place instantly. In this time, memory T cells do their jobs. "When re-exposed to a virus or booster, these cells will kick into overdrive. In a 24-hour period, you can get a tenfold increase in the number of your memory T cells," the study said.
10. Several studies have found that people who had been vaccinated or had been infected with SARS-CoV-2 had about the same T-cell response to Omicron as they did to the Delta variant, despite a large number of mutations.