I have been toying the idea of fusing our white blood cells which search and destroy malicious foreign bodies with artificial intelligence to fight various disease causing pathogens, my worry is that nano machine is just too small to house A.I. otherwise with machine learning that mimics our brain function those white blood cells can easily and accurately identify suspicious activity and intervene quickly before damage can be done. Is this feasible in the near future or impossible due to too many engineering challenges ahead?
First off, white blood cells operate autonomously and in small nodes, not collectively like an organ. If you were going to have them act under intelligent guidance, you would need a central control area (call it a symbiont) with intelligence that detects threats and operates under a program to eliminate them. With modern gene therapy, it's not so far-fetched.
-It would be bioelectrochemical, biochemical and/or biological, communicating with/controlling the subunits (call them nano-whites) with hormonal-type signals to seek out cancers, parasites, viruses, and pathogenic bacteria an coordinate strategies. A small computer could even be installed - the symbiont would control the immune response to the implant, so there would be no rejection.
-A symbiont would rely on a lot of the same strategies that our immune system does (initially), but would coordinate the response more efficiently and would (hopefully) be smart enough to avoid auto-immune responses.
-If the symbiont were somehow connected to an external input (a wireless bio-powered receiver, for example) then you could transmit the code for a new virus, and the symbiont could be ready for it before the person even encountered the illness. As scientists devised new engineering strategies to deal with disease, they could upload these to the symbiont, who could then custom genetically engineer nano-whites to new tasks.
-A symbiont could be programmed/grown to recognize an original central body plan for the individual and coordinate nano-whites and stem cells to lay down new extracellular matrix and regrow/regenerate old/damaged organs or even lost limbs.
- This level of input would come at a potentially terrifying cost. Inputs could tell the symbiote to recognize yourself as foreign, or attack/modify specific parts of your body (remove impulse control, modify memories(?), convert you into something not-human, etc. all ordered externally. Imagine a government increasing the expression of a gene controlling religiosity, or altering sexual orientation post-developmentally, or manufacturing new stem cells to slowly start converting you into an extraterrestrial? What if the nanites were a "gift" of aliens curing disease while quietly conquering us? The possibilities are endless.
The immune system already has a kind of AI built in. It learns via exposure and reacts to reexposure based on what it learned before. But I think individual cells might be too small to host an intelligent network. WBC only live a fortnight and a half or so: engineering a neural network into something that's only going to last a short while might be a waste.
What you might consider is using nano machines to rewrite the WBC construction subroutines at the genetic level and the antigen expression subroutines systemically. You'll want to enhance the "I'm a safe self-body-part" antigens that all body cells exhibit in the presence of WBC. Kind of like a national ID card. This ought to decrease the possibility of pathogenic mimicry.
In addition to enhancing the native immune response, you might consider keeping the AI outside the body and using it to engineer a small, easily implantable, easily extractable, organ whose cells express "I am self" to the immune system, but are designed to produce and release at intervals a suite of known antigens from an external library.
This wouldn't confer super immunity at first sight of a new pathogen; but it would ensure improved immunity against anything known and in the library.