COVID-19: Separating Fact from Fiction

by Anirban Mahapatra

By infecting a host cell that has an ACE2 receptor, SARS-CoV-2 causes it to sound the alarm to nearby cells. The host cell does this by undergoing a kind of programmed cellular suicide. The signals released are its swansong: they’re recognized by nearby cells, which generate signalling molecules called cytokines. Then, these new signals call in the immune force—monocytes, macrophages and T-cells to the site of the infection. In a healthy immune response in most people, the virus-specific T-cells are attracted to the site of infection where they eliminate the infected cells before the virus spreads. Antibodies block viral infection. All the neutralized viruses and dead cells are recognized by alveolar macrophages, which clear them out. There’s minimal and reversible damage to the lungs. Patients with functional immune systems and without obvious risk factors can generate healthy immune responses that quash the virus before COVID-19 progresses to a severe phase. In a dysfunctional immune response, cells build up in the lungs without being cleared. This causes many cytokines to be produced and they turn on lung infrastructure, thereby causing destruction. These cytokines also circulate to other organs where they can cause multiple organ damage. If there are antibodies that cannot neutralize the virus, they can boost infection instead of warding it off. The sea of cytokines released by the immune system results in something called the ‘cytokine storm’.11 An abnormally low lymp...