Most biologists believe that the immune system's defense against infections largely rests on its ability to distinguish self molecules from non-self molecules. This concept seems central to our understanding of immune function. Several immunologists developed an alternative hypothesis: that the immune system's effectiveness rests mostly on its ability to recognize damage to body tissues caused by the invaders, not on the ability to recognize non-self. If you were going to test the "damage" hypothesis, what might you look for? Which type of cell would you expect to be directly affected by damaged tissues? Why? Some proponents argue that the damage hypothesis makes more sense from an evolutionary perspective, claiming that it is more advantageous for an organism's defense system to respond to tissue damage than to the mere presence of a foreign microbe. Do you agree? why/why not?
To test whether the damage hypothesis is correct, you would need to look for factors produced by the host, not the microbe, that are capable of inducing an immune response. If these molecules were injected into an animal, together with a foreign protein or microbe, they would induce a much stronger immune response than the foreign protein alone, thereby showing that these molecules were largely responsible for inducing a strong immune response. One such ...
This solution details how the immune response can discriminate between normal cells and infectious agents. Self/non-self discrimination is explained, in addition to how pattern recognition receptors relate to the 'danger hypothesis'.