So what are you proposing? Trying to avoid everything that might cause an immune system reaction? That will eventually lead to the immune system really running amok...
For example, Dectin-1 is one of many innate cellular receptors that launch inflammatory responses when Bread yeast (and others) is detected (and possibly 1,3 beta glucans from wheat). We are in a genetic war with saccharomyces cerevisia, inside of our DNA. And not just us, all animals need to be in this war, because otherwise we'd die.
https://en.wikipedia.org/wiki/CLEC7A
So if all this is true, does it make sense to put yeast extract in your gravy tonight?