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.

Neutralizing antibodies

• 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.

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