How can we break the hegemony of this preceived, majority view that the "purpose" of the adaptive immune system is to eliminate "non-self"?
"The human immune system is designed for protection against invading pathogens."
This quote from a 2019 article emphasises how this perception hangs on – like some hideous, gigantic limpet.
("Pathogens" here, I am sure, refers to disease causing micro-organisms. Full stop.)
If, as I suspect, writers of such statements believe that the adaptive immune system "is designed to protect against invading pathogens" (disease causing micro-organisms) then, I contend, this is fundamantally wrong – and not just because of the teleology of "designed".
Let me re-emphasise, first, where the "attack" on foreign organisms orginates. Free living amoebocytes (from which all multicellulate metazoans evolved) have to find and ingest "fuel" so that they can metabolize, grow and reproduce. They have a well evolved sense of what constitutes an appropriate menu and it, necessarily, includes other living organisms and/or their decaying debris. In mammalian immune systems, this core function is maintained and used as the basis for the acquisition of energy and other essential resources. Whenever we see "attacks" on (micro-)organisms, the immune system is ultimately reverting to this primaeval behaviour.
Now, the next point is critically important. Effete self cells (eg, dying, damaged, aging, infected) constitute, by far and away, the largest volume of debris that needs to be managed and reassimilated in a vertebrate body. What the adaptive immune system facilitates is a mechanism to remember the context of these cell deaths and the resulting debris. Tidy and neat death plus disposal (by apoptosis and "eat me" signalling to phagocytes) need not provoke any panic. Indeed, these encounteres are probably remembered as "safe debris" (if you come across it again, "tolerate it and subdue/avoid any inflammatory responses"). Catastrophic and unexpected death is undesiraeable and any re-encounter is best remembered as an event that warrants an aggressive inflammatory response (to both the self-cells and the associated debris - that could well contain bits of miro-organisms). So, the adaptive system is predominantly managing the inflammatory response to self-cell death (predominantly deployed here because the catastrophic demise of foreigh cells/bacteria may well release similar alerting molecules).
So, the the adaptive immune system is a "pathogenic-event/non-pathogen-event" classifier. But the pathogenic agent (a pathogen) can be biotic (bacteria, virus, fungus etc) or abiotic (physical agents like heat, impact, radiation, irritant chemicals, toxins, sunlight, heavy metals, asbestos etc, etc). The progressive highjacking or "pathogen" to mean, exclusively, a damaging micro-organism has caused enormous confusion and harm.
I will be happy when an article appears in which the "purpose" of the immune system is restated in a paraphrase of what follows;
"The purpose (OK – I know – it's a teleology) of the immune system is to manage all disruption in the colony of cells that constitute an animal. It does so by responding appropriately to the various forms of tissue disruption and of self-cell death. It manages and classifies the debris, it remembers the context of prior encounters and it sets the system on a course to regenerate and restitute tissue structure and function. It is mobilised in all pathogenic events."
So, the immune system (morphostatic system I would prefer to call it) is mobilised and involved in obesity, anxiety, schizophrenia, dementia, atheromatous disease, injury, fractures, cancer and just about any other disease you can mention.
Oh, I forgot to include infection. Silly me.