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SARS-COV-2-SPECIFIC T CELL IMMUNITY

Focus: GS-III Science and Technology

Why in news?

  • A recently published research paper says natural exposure or infection with the novel coronavirus may “prevent recurrent episodes of severe COVID-19”.
  • This is because, once infected with SARS-CoV-2, the immune system elicits “robust, broad and highly functional memory T cell responses”.

Details

  • The study found SARS-CoV-2-specific T cells even in family members who have been exposed to the virus but have tested negative on antibody blood tests.
  • SARS-CoV-2-specific T cells were also seen in convalescent individuals with a history of asymptomatic infection and mild COVID-19 disease.
  • All categories of people — recovered from moderate or severe COVID-19 disease, or in the convalescent phase after mild or severe disease or exposed family members or healthy people — exhibited “robust memory T cell responses months after infection, even in the absence of detectable circulating antibodies specific for SARS-CoV-2.
  • This indicates a previously unanticipated degree of population-level immunity against COVID-19.
  • This implies that seroprevalence (the level of a pathogen in a population, as measured in blood serum) as an indicator may underestimate the extent of immunity in the population.
  • Even as antibodies wane with time, robust T cell memory formed after SARS-CoV-2 infection suggests that “potent adaptive immunity is maintained to provide protection against severe re-infection”.

Recently in news: Serological survey in Delhi

What was the serological survey about?

  • The serological survey was meant to detect whether the person being tested had developed antibodies against the coronavirus.
  • Since it is not possible to test everyone, detecting antibodies in random sets of people is an indirect way of estimating the extent of disease spread in a community.
  • The antibodies are proteins produced by the immune system to fight external organisms like viruses that try to enter the body.
  • These are produced only after the infection has happened, and are specific to the attacking virus or bacterium.
  • The presence of antibodies, therefore, is an indication that an infection by that particular virus or bacterium has already occurred.
  • Subsequent attempts to infect the body can be thwarted by these antibodies.

Do antibodies ensure Immunity?

  • The mere presence of antibodies does not mean that the person is protected against the disease.
  • What is also important is the amount of antibodies present, and whether it also includes what are known as “neutralising antibodies” which actually fight the disease.

-Source: The Hindu

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