Recent studies have found that antibodies to the novel coronavirus that causes Covid-19 decline rapidly. In other words, immunity to Covid-19 could likely be lost within months of being infected. This could have implications for vaccine candidates currently undergoing human trials.
Another component of the immune system, T-cells, a type of lymphocyte or white blood cell, is also in focus. Studies have shown evidence of T-cell reactivity against SARS CoV-2 – the novel coronavirus at the centre of the current outbreak – in people unexposed to it.This has resulted in speculation that these are ‘memory T-cells’, developed after exposure to other coronaviruses that cause the common cold, and could offer protection against SARS CoV-2.
In this interview with Scroll.in, Dr Vineeta Bal, immunologist from the Indian Institute of Science, Education and Research, Pune, explains the complex human immune system, unpacks research on the immune response to SARS CoV-2 and weighs in on claims that Indians have innate immunity against the virus.
What is the difference between innate and adaptive immune systems? These are the two main components of the immune system. Innate immune system comes into action within minutes of any invasion: be it by a virus or a bacterium or anything. So within minutes of the invader breaking the skin barrier or the gut lining or lung lining – if any of this is breached and the invader is inside the body – the cells and other proteins that respond are part of the innate immune system.
The innate immune system does not recognise, necessarily, one virus as distinct from the other. For example, whether the invader was SARS CoV-2 (the novel coronavirus which has caused Covid-19) or SARS CoV-1 (Severe acute respiratory syndrome coronavirus which caused the SARS outbreak in 2003) or MERS (another coronavirus responsible for the Middle Eastern Respiratory Syndrome) or flu, the innate immune responses would be pretty much similar.
Both antibody response and T-cell response are part of the adaptive immune system. Antibodies are the proteins that are synthesised by the body. They are normally called immunoglobulins,he adaptive immune system stacks away some of its supplies, which is the T-cells that are generated or are triggered by the presence of the virus, for the future. This is called immunological memory or memory T-cells. So, a large number of T-cells, whether helper or killer, will be used up if the infection is severe, a small portion of the ammunition (T-cells) is kept in reserve, so that once this virus attack is over, these extra cells will remain as back up. These will be specific to SARS CoV-2 in this case or if it were a Japanese encephalitis infection, then the memory T-cells will be specific to Japanese encephalitis and are unlikely to provide protection to other viral infections.