According to a recent study, “High levels of a molecule seen in severe COVID-19 patients may prevent them from developing long-term immunity to the novel coronavirus”. This is because severe COVID-19 Patients produce a very few of the type of B cells which are responsible for generating antibodies against the virus.
High levels of cytokines present in severe COVID-19 patients increases the inflammation due to which immune cells start to produce more cytokines. This process is known as cytokine storm. Due to Cytokine storms, COVID-19 patients are likely to be unable to develop long-term immunity.
Study author Shiv Pillai from Harvard University said, “We’ve seen a lot of studies suggesting that immunity to COVID-19 is not durable because the antibodies decline over time. This study provides a mechanism that explains this lower-quality immune response”.
In a previous study, which involved mice infected from diseases which led to the occurrence of Cytokine storms, researchers found that TNF (one of most abundant cytokines released) appeared to block the formation of germinal centers where B cells mature and generate antibodies. Germinal Centers lie within the lymph nodes and spleens. These infected mice who had their TNF gene deleted when given antibodies to block TNF, the germinal centers were able to form. The study suggests that TNF is likely to be responsible for preventing the germinal centers from forming in people suffering from the infection like coronavirus.
Researchers have also found high levels of TNF present in lymph nodes of dead COVID-19 patients.
Study Author, Robert Padera said, “When we looked at the lymph nodes and spleens of patients who died from COVID-19, including some who died very soon after getting the disease, we saw that these germinal center structures had not formed”.
In coronavirus patients, who were unable to form germinal centers but had immune response present in their bodies, researchers found that in such patients active B cells could still help in producing some neutralising antibodies against the virus.
According to the scientists, without the presence of germinal centers, the immune system of coronavirus patients may fail to develop long-term memory to the virus. Pillai commented that coronavirus patients are likely to get infected again with the same coronavirus three or four times in the same year.