My daughter asked a question that I could not answer.

If you have a cold, you have symptoms such as fever, cold and sore throat. These symptoms, however, are the reactions of the immune system to bacteria, viruses and other germs.

So my question is: What would happen if the immune system did NOT respond? I know that bacteria can produce certain poisons. And viruses can capture human cells and make them produce more viruses.

Now to the naive part: But what's wrong with that?

  • Are Viruses dangerous because these cells would then no longer perform their function?
  • Without any immune system: Would a virus simply take over all human body cells?
  • Is it not the organism in the first place, who puts itself in mortal danger (such as high fever or inflammations) because of the defense reaction?


  • $\begingroup$ I hate to say it but, it depends. There may well be some pathogen which would otherwise be harmless, if not for the body's defense mechanisms. However, we are talking about a system which has evolved over thousands of years. In turn, the pathogens have also been evolving for thousands of years. There have been countless variations over the years. One thing is for sure, people who have an issue with their immune systems tend to die from pathogens which people who have healthy immune systems do not die from. $\endgroup$ – takintoolong Nov 26 '18 at 2:13

Basically you would rot from the inside out, as bacteria and viruses destroy your cells.

Fever is your body using heat to denature the viral proteins (viruses don't have chaperone proteins like us so they are more vulnerable to heat) Sore throat is you body killing infected cells before the virus can reproduce inside them, normally the virus will reproduce inside the cell until the cell bursts or simply runs out of resources and dies both release huge numbers of the virus.

Check out the virus life cycle. https://en.wikipedia.org/wiki/Viral_life_cycle

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