From UPSC perspective, the following things are important :
Prelims level : T-Cell Immunity
Mains level : Long term health impact of COVID
A new study from Wuhan has studied the role of T-Cell Immunity against prolonged and sever COVID-19.
What are T-Cells?
- Like B cells, which produce antibodies, T cells are central players in the immune response to viral infection.
- For your immune system to fight off any kind of invader, such as a virus, you need a kind of white blood cell called a B cell, which makes antibodies, and a similar-looking white blood cell called a T cell.
- T cells can play different roles altogether.
- They can act as “killer cells”, attacking cells which have been infected with a virus or another kind of pathogen, or they can act as “helper cells” by supporting B cells to produce antibodies.
How do they function?
- Alongside antibodies, the immune system produces a battalion of T cells that can target viruses.
- Some of these, known as killer T cells (or CD8+ T cells), seek out and destroy cells that are infected with the virus.
- Others, called helper T cells (or CD4+ T cells) are important for various immune functions, including stimulating the production of antibodies and killer T cells.
- T cells do not prevent infection, because they kick into action only after a virus has infiltrated the body. But they are important for clearing an infection that has already started.
- In the case of COVID-19, killer T cells could mean the difference between a mild infection and a severe one that requires hospital treatment.
What did the latest research find?
- The researchers found that neutralising antibodies were detectable even 12 months after infection in “most individuals”.
- It remained stable 6-12 months after initial infection in people younger than 60 years.
- The researchers found that “multifunctional T cell responses were detected for all SARS-CoV-2 viral proteins tested”.
- And most importantly, the magnitude of T cell responses did not show any difference immaterial of how severe the disease was.
- While the ability of antibodies to neutralise was nearly absent against the Beta variant, it was reduced in the case of the Delta variant.
- SARS-CoV-2-specific neutralising antibody and T cell responses were retained 12 months after initial infection.
- Neutralising antibodies to the D614G, Beta, and Delta were reduced compared with those for the original strain, and were diminished in general.
- Memory T cell responses to the original strain were not disrupted by new variants.
- The findings show that robust antibody and T cell immunity against SARS-CoV-2 is present in majority of recovered patients 12 months after moderate-to-critical infection.
Robustness of antibodies
- The study reveals the durability and robustness of the T cell responses against variants, including Delta, even after one year of infection.
- Most importantly, the robust and longstanding T cell responses were seen in people who have not been reinfected or vaccinated.
- This would mean even in the absence of vaccination, a person who has been infected by the virus even one year ago would have robust immune responses.
- It would offer protection against disease progressing to a severe form requiring hospitalization.