Diminishing antibodies

Subject: Science and tech

Context:

• Delhi’s third sero-surveillance report threw up a surprise of sorts, with the overall seroprevalence falling. According to experts this could be attributed to “diminishing antibodies”.
• A significant decrease in seroprevalence was seen in Northeast, North and Central districts as per the survey report, while a slight increase was seen in South, East, West, and North West districts.

Concept:

• The immune system is made up of two parts: innate immunity and adaptive – or acquired – immunity.
• The innate immune system, which includes white blood cells called dendritic cells, monocytes and neutrophils, is present at birth and responds instantly to invaders. This group of white blood cells bombard pathogens with destructive chemicals and swallow and destroy viruses and bacteria. The innate immune system provides an instantaneous reaction to a pathogen. The problem is that it’s a blunt instrument – it responds the same way to all perceived threats.
• The adaptive immune system, which is made up of B cells and T cells, must learn about a pathogen and its characteristics from the innate immune cells. This system takes longer to kick in, but the up side is that it is very specific and in many cases lasts a lifetime.
• The history of pathogen exposure is carried in so-called memory T cells and memory B cells. When an infection is defeated and gone, these cells reside in the peripheral tissues of the body such as lymph nodes or spleen and serve as a memory of the disease-causing virus. This immunological memory is responsible for the host defense and kicks into action in case of the second wave or attack of the pathogen.
• It is normal for antibody levels to decline after a person has recovered from a disease.
• Antibodies are proteins and last for only between three and four weeks in the blood circulation.
• To keep antibody levels high, B cells need to replenish them with a fresh supply.
• But in COVID-19, the declining antibody levels suggest that the cells that produce these antibodies are not present in sufficient numbers, which would explain the drop in antibody levels.