Why in News?

• A recent serological survey done by the Delhi government for patients in Delhi revealed that seventy-nine of 257 people who had COVID-19, recovered, and later tested for antibodies against the virus, did not have the antibodies.

Findings of the study

• 30% recovered COVID-19 patients have no antibodies. 
• Experts, however, said that there was no need to panic, as the neutralising antibodies (IgG) tend to vanish after three months, but in most cases the memory cells will remember the virus and trigger an immune response if the person who recovered from COVID-19 is again attacked by the virus.

Memory Cells

• B cells and T cells are the white blood cells of the immune system that are responsible for adaptive immune response in an organism.
• Both the cells are made in the bone marrow. B cells mature in the bone marrow while the T cells travel to the thymus and mature there.
• In most cases, the antibodies (IgG) decline by three months, but memory B cells and memory T cells store the memory of the virus. They activate the immune mechanism when there is a re-infection.

Reference:

1. https://www.thehindu.com/news/cities/Delhi/30-recovered-covid-19-patients-have-no-antibodies-govt-survey/article32604536.ece