4 ms·
Because it's part of the arms race with pathogens that has been going on for a billion years since multi-cellular life first appeared. Pathogens do lots of ver
by Enginerrrd 7y ago
Because it's part of the arms race with pathogens that has been going on for a billion years since multi-cellular life first appeared. Pathogens do lots of very clever things to hide from the immune system, so the immune system is tuned to detect very subtle changes. The body largely operates on zero-trust network models, except for a few locations where the benefit of a too-active immune system has serious consequences to the fitness of the organism. The eyes and the testicles are good examples of that in humans.
- asveikau 7y agoI guess auto-immune disease is an example of where it also goes the wrong way for somebody. Probably most of us know somebody with IBD, lupus, or any of the others. It's very common for the body to reject something benign, or ourselves.
- friedegg 7y agoType 1 diabetes is a good example of this, where the body detects its own insulin producing cells as threats and eliminates them. Lots of the research in type 1 treatments isn't just about producing insulin, but figuring out how to prevent the body from destroying it again without all of the risks of immunosupressant drugs.
- wongarsu 7y agoTo add to this: if the immune system would just check that the cell is human then every invader would just evolve to pass that check. The only viable way to defend is to mark the cells as belonging to this specific human. That way even if some bacteria evolves to trick my immune system it's unlikely to also trick yours, and the infection can't spread.
- alan-crowe 7y agoAdditionally, if the immune system would just check that the cell is human, then humans would be vulnerable to contagious cancer, such as the facial tumor disease suffered by Tasmanian Devils https://en.wikipedia.org/wiki/Devil_facial_tumour_disease https://en.wikipedia.org/wiki/Devil_facial_tumour_disease
- mkl 7y agoHumans almost certainly are vulnerable to contagious cancer (there are a few known in other species: https://en.wikipedia.org/wiki/Clonally_transmissible_cancer https://en.wikipedia.org/wiki/Clonally_transmissible_cancer) . We just haven't acquired/discovered any yet.
- apathy 7y agoHTLV, EBV, HPV you better believe we have! It’s just rare (thank goodness).
- skosch 7y agoThose are cancers caused by viruses, and it's the viruses getting transmitted. On the other hand, clonal transmission refers to the cancer cells themselves leaving sick individual A, entering healthy individual B, and continuing to reproduce there.
- apathy 7y agoYou could use transmissible preleukemia (eg CHIP in allo transplants) as an example if you wished. Direct unassisted clonal transmission in humans seems likely but, as you noted, it hasn’t been documented to the extent that Tasmanian Devil facial tumors have. Warts are a corner case. I’m not sure whether it’s been determined if some hosts end up increasing the fitness of the shed cells. If so, that’s quickly heading towards a globally transmitted precursor lesion.
- darkerside 7y agoThis weirdly reminds me of public private key authentication
- jacobolus 7y ago> except for a few locations where the benefit of a too-active immune system has serious consequences For anyone else curious about this, https://en.wikipedia.org/wiki/Immune_privilege https://en.wikipedia.org/wiki/Immune_privilege