IAS Gyan

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Unexposed people may have COVID-19-specific memory T cells

15th July, 2020 Health


Recent studies have shown that people unexposed to and not infected with novel corona virus may still exhibit T cell responses specific to this virus.

Reasons behind these T-cells:

  • SARS-CoV-2-specific T cell responses seen in healthy people might arise from memory T cells derived from exposure to ‘common cold’ corona viruses.


  • Whether the presence of pre-existing immunity from memory T cells offers clinical relevance — to protect or even harm people — when exposed to novel corona virus is not known.
  • “Pre-existing T cell immunity to SARS-CoV-2 could be relevant because it could influence COVID-19 disease severity.
  • It is plausible that people with a high level of pre-existing memory CD4+ T cells that recognize novel corona virus could mount a faster and stronger immune response upon exposure to the virus.
  • There is a possibility that pre-existing T cell memory might influence vaccination outcomes.
  • Pre-existing immunity could help elicit better immune responses against novel corona virus, and these responses can manifest faster.

About T-cell and its Role:

  • T cells (also called T lymphocytes) are one of the major components of the adaptive immune system.
  • Their roles include directly killing infected host cells, activating other immune cells, producing cytokines and regulating the immune response.
  • T cells originate from haematopoietic stem cells, which are produced in the bone marrow.

Reference: https://www.thehindu.com/sci-tech/science/unexposed-people-may-have-covid-19-specific-memory-t-cells/article32052605.ece