[nextos]

I also found it a bit too philosophical in the sense that we can already explain a lot of the variations in outcomes to infection.

For example, HLA/MHC is a family of genes tasked with the presentation of antigens (e.g. chunks of proteins) from pathogens and your own cells to the immune system. It is a very polymorphic region, i.e. full of genetic variants that lead to lots of differences in the peptides that are presented, to stop spread of infections at population level.

If you have one of the lucky/unlucky alleles, you will have high chances of protection/susceptibility. Some alleles, like HLA-B57, protect against HIV but it's a tradeoff. Carriers are much more susceptible of autoimmunity [1].

From an environmental point of view, if you have dysbiosis, e.g. if your gut microbiome ecology is altered, T cell receptor distributions will be altered and you are more likely to have a bad response to certain infections.

[1] Effects of thymic selection of the T-cell repertoire on HLA class I-associated control of HIV infection. https://www.nature.com/articles/nature08997