T-cell immunity and COVID-19

Context

• In COVID-19 infection, T-cell immunity is more long-lasting than antibodies. It resides in a subset of white blood cells called T-lymphocytes, or T cells.

What are two types of immunites?

1. Innate immunity- It is an immediate response, not strong enough to prevent pathology if the virus is highly virulent or the ‘inoculum’ (infecting virus load) is heavy.
2. Adaptive immunity- It takes several days to develop and become effective. It has two arms antibodies and T-cell immunity.

What are T cells?

• A T cellis a type of lymphocyte, which develops in the thymus gland and plays a central role in the immune response.
• T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor on the cell surface.
• T – cells are developed in –i) CD8+ T cells, also known as "killer cells", are cytotoxic and ii) CD4+ T cells which function as "helper cells".
• Unlike CD8+ killer T cells, these CD4+ helper T cells function by indirectly killing cells identified as foreign:

T-cell and testing

• The test known as ‘T- SPOT test’ for assessing T-cell immunity is complicated and expensive.
• T-cell immunity is a better and more durable marker than antibodies of past infection for this novel virus.