An overreacting immune system is one that reacts in a manner that is disproportionate to the threat. The cytokines are an essential component of immune system function, so the very fact that they go into overdrive is the sign that that person’s immune system is too strong. In my opinion, it is not necessarily a sign of dysfunction but rather that on a graph of amplitude of immune (cytokine) response, those people’s immune systems would fall on the right side of the bell curve.
In the 1917-1919 H1N1 pandemic, the number of deaths was driven up by the numbers of young healthy people who succumbed to cytokine storm. My stepdad’s mother died of it.
Of course there is a lot we do not know about immunity. For example, what do we know about why a very small number of people develop Guillaum-Barre syndrome after exposure to certain pathogens, notably influenza?
There are some observations that should be noted and remembered.
The body itself has not really changed that much since 1917, but our food and exposure to chemicals have.
At times, “Today’s problems were yesterday’s solutions.”