Thank you for the mention; I’m certainly honored. This is perhaps one of the most interesting hypotheses that I’ve come across. Exosomes and viruses seem to bear huge similarities, so they might somehow be related. While the first part of the theory is substantiated, the second part where the immune system expels the virus/exosome to prime others’ immune system to prepare against the toxin can be countered, I think.

First, given the vast types of viruses (and diseases they cause), it’s hard to think there would be as many different types of environmental toxins as well. Second, evolutionarily speaking, people tend to avoid people who are sick (if I’m not wrong). As follows, thirdly, what happens to those who don’t contract the virus? Does that mean that person now lacks protection against the environmental toxin or starts expelling the same virus/exosome?

I think these questions cannot be scientifically tested, at least with the current technology. To test it, a specific environmental toxin has to be exposed to a mouse, for example, and more sophisticated technologies are required to ‘capture’ the exosome and analyze it. Maybe this is the main reason why it remains a theory as there’s no way to test or experiment it.

But it would be life-changing if the above questions can be answered in favor of the hypothesis. And remember, I’m a mere postgrad (MSc-PhD) student so please be aware that my answer is not at the professorship level. Still, thank you, Matthew Bottomley, for your thoughts as they’re certainly eye-opening, giving me a completely different viewpoint of looking at the microbial world :)