It is pretty clear that the immune system plays a crucial role in how you recover from the virus.
In fact, the majority of coronavirus-related deaths are due to the immune system acting in its reaction to its own self, not to the virus itself causing damage. And what happens when you have the virus in your body and who is at risk of developing a more serious infection?
When you are infected for the first time, your body activates the normal innate immune response as it does with any virus. The first molecules which are released to fight the virus are called cytokines. Ideally, this initial reaction helps the body to rapidly take control of the infection, while the virus has its own defenses to prevent the impact.
The aim of the immune system is to trap the virus and allow it from spreading too widely so that the second phase of the immune system has enough time to kick in before things get out of control.
The virus can multiply and spread quickly in certain patients, though, until the immune system brings it under control. One explanation that can happen is because a huge number of viral particles infect the body. The more viruses there are, the more difficult it is for the immune system to handle.
If the virus can stay in the lungs, the disease can progress toward pneumonia as more cells are infected and inflamed. The infection does some of the damage, but a much bigger portion is due to the immune system itself attempting to kill and get rid of those infected cells.
The disease will now go in two ways at this point: the immune system will recover and reclaim control of the virus, ultimately removing it through the action of T cells and antibiotics.
Or the immune system will freak out and start over-responding, churning out ever more inflammatory proteins, called cytokines, in a relentless effort to wipe out the virus.
This is this second path that causes serious cell death in the lungs, resulting in the most extreme illnesses, conditions of acute respiratory failure, and even death.
In the time being, the best defense against the infection is to help the digestive system with sleep, exercise, and proper diet and, most importantly, to wash your hands and maintain social contact so that you are not infected.