Thanks for your interest!

All humans bring along their own set of genes, and so we all react differently to our environment. When talking about toxicology, the most important genes are always those involved in the so-called "xenobiotic metabolism", as they determine how fast your body can detoxify and dispose of uptaken toxic chemicals (to simplify it a lot^^). There are big differences between humans in that regard.
However, I doubt there is really someone who is "not susceptible" to mold toxins at all.
"The dose makes the poison". At a certain concentration, everyone suffers. But of course: A dose that might be dangerous for one can be irrelevant for another person. And vice versa.
We are aware of that, and there are measures that are taken to account for hose differences in risk assessment of chemicals. But I would have to write a full post if I would have to explain those in detail. ;-)