# Immune resistance to biological colonisation

I'm thinking of a plot where the Earth is taken over and literally eaten by a race of giant alien beings who use mass-energy conversions to power themselves (These guys are as big as the sun, body structure of StarCraft Leviathans, sentient)

Without a home, humanity takes it upon itself to do the impossible: colonise the bodies of the beasts themselves.

Now, the aliens have discovered machine augmentation. They lack limbs, but instead use long tentacles as graspers. They suck material from heavenly bodies through a toothless mouth, and their stomach functions as a mass-energy reactor, with the aid of a particle-accelerator type environment, where they collide the particles and utilise the Hawking radiation to power themselves.

The plan of the protagonists is to enter using special drop pods along with the material, latch onto the oesophagus wall, burrow into the muscle and deploy a colony there. The damage will be smalller than a pinprick for the giants, and they won't even notice. However, the immune system will.

So, my question, what kind of punches would the immune system, biological or semi-mechanical, have to pack to present an actual threat to the human drop pods or the people themselves?

Extra info:

• The aliens do generate their own gravitational field.
• Humanity's technological level is sufficient to allow interplanetary travel.
• The immune system cells of the giants are likely to be bigger than the people or their drop pods.
• The humans are carrying a military force, including heavy artillery, armored vehicles, and troop transports.
• I've experience with Star Craft, still I have 0 idea how large those Leviathans are. Please specify the dimension instead of referencing something else most people have no clue about. Also I read the question as "what is about the size of humans or smaller and can harm humans?" to which the answer is a zillion different things and ,tbo , this is also trivial to answer. It would be nice if you could give some sort of direction you want to go into and why it is a problem for you to come up with options yourself – Raditz_35 Mar 1 '18 at 11:53
• StarCraft Leviathans are generally moon-sized, but these guys are bigger. However, they share approximately the same body structure. starcraft.wikia.com/wiki/Leviathan I recognize that there are a lot of things that can harm humans, but I need stuff a normal cell would have, like enzymes. I really can't strap on some teeth or claws to a lymphocyte, can I? – Budhaditya Ghosh Mar 1 '18 at 11:58
• Why not? If it is vs smaller animals like humans, why can't they have such an immune system? Perhaps even another humanoid species that lives in symbiosis. And I'm sure you are aware of poisons? Carbon monoxide perhaps? It can be used to flood the area. Several proteins are poisonous as well, prominently en.wikipedia.org/wiki/Botulinum_toxin . And if they are mechanical, they can be anything. Also if they have an immune system vs humans, they must regularly encounter similar threads. What are those? – Raditz_35 Mar 1 '18 at 12:10
• Immunity is cell-mediated. Any sort of physical defense will require multi-cellular structs which will lose their ability to move freely throughout the body. If we release poisons into the body, we run the risk of harming the very thing we intend to protect. To deliver poisons like botulin or ricin or anything, we need to pierce the skin or armour, which is again impossible without mult-cellular structs. – Budhaditya Ghosh Mar 1 '18 at 12:15
• Ok, I get that, you want to know how giant regular cells can combat humans, however you state "semi-mechanical" how does that all fit together? Btw it is a good idea to edit your original post for clarification since nobody can be bothered to read the comments. Also please note that a poison does not need to be poisonous to the host, especially in small quantities compared to their size.A moon-sized organism shouldn't have any trouble flooding a couple of square metres even with something like chlorine or hydrocyanic acid – Raditz_35 Mar 1 '18 at 12:22

Such a being would not be made out of matter as we know it, because matter on the scale of a planet, let alone a star, cannot maintain a structure like that.

Gravity will turn anything the size of a planet into a planet, and anything the size of a star into a star. Stars keep themselves from collapsing further by using fusion, and eventually electron degeneracy (white dwarf phase) or failing utterly (supernova).

Chemical bonds, the kind of thing that lets you form life on earth, just doesn't matter at these mass-energy-force scales.

Planets keep themselves up via chemical bonds, no chemical force can prevent them from forming a sphere.

You'll have to presume something else keeping it together. Well, really apart.

So one approach would be to posit a serious island of stability in the post trans uranics with frankly insane properties. These post trans uranic elements would be nearly impossible to form without a K3 or higher civilization doing so on purpose; no natural process generates this matter, including supernovas and neutron star collisions, so doing so will require insane energy scales and careful nuclear chemistry.

Given this handwavium matter, you could give it a form of chemistry that can stand up against planetary or stellar gravitational gradients. The beings wouldn't look like scaled up terran life forms (because why would they?).

Even if we assume these beings are extremely low density, they are going to be insanely massive. Moving such a being through insterstellar space is a task for a K3 civilization.

Eating a planet the size of Earth is E41J, Jupiter is E44J. A K3 civilization consumes E36J/second; it has to convert a Jupiter-sized body to energy every 3 years.

Getting one of these creatures up to 1% of lightspeed is going to require converting mass-energy on the scale of 0.5% of its mass (at 0% loss) to energy. Stopping at the other side a similar amount. And this ignores the rocket equation. Probably you'll end up building two or more mirrors and bounding lazer light repeatedly between them to extract max momentum to stop at a new star.

Regardless, these creatures form a K3+ civilization (each one of them is beyond K2). The stuff they are made out of is going to be effectively invulnerable to anything up to and possibly including nuclear weapons in order to be strong enough to maintain a structure at these scales.

They probably have an immune system consisting of other sentient races that have taken up residence on the creature. Having an atmosphere when the creature is the size of a star is going to be impractical without it forming a star on the surface of the creature, so the sentient races are going to be vacuum adapted somehow. The creature itself probably won't care about the humans, but instead the current residents will resist being invaded by johnny-come-lately.

Minimal amounts of structure made of ordinary matter will accumulate on the surface; the creature has to keep that under control, as it probably doesn't want it to undergo fusion or the like.

Such creatures won't be interacting with things with "tentacles" or "sucking". It might drop a spore creature on a planet, which proceeds to build a total conversion reactor. Possibly it builds a beanstalk and pumps matter out of the gravity well powered by said total conversion. Once in orbit, the matter is ferried into the maw of the creature.

The planet Earth will mostly be an appetizer compared to the real treat of the solar system; Jupiter. Almost all of the mass of the solar system is in Jupiter, and given the level of arcane alchemy required to maintain such a creature, the difference between Earth and Jupiter matter is not all that interesting.

The civilizations living on this K3 civilization creature could easily be K2 civilization level without the actual creature even noticing the parasite load. A K2 civilization (a civilization that has enclosed their star in a dyson sphere and uses all of the energy efficiently) is going to use something like 0.00000001% of the energy that this creature processes during feeding times.

If your humans are just starting out of Earth's gravity well, they are going to be K1 or so. They may not be in the same league as even the ignored parasites on the large planet eating creature. A full K-type difference is like the difference between an uncontacted tribe on a small island, and the modern US. There wouldn't be a conflict.

In short, I don't think you understand how a really impressive a feat a macro-scale "biological" creature is. They are going to be sufficiently advanced technology.

Reality check won't be kind to this idea.

The short version is that your planet killer requires handwavium and lots of it.

the Earth is taken over and literally eaten by a race of giant alien beings who use mass-energy conversions to power themselves (These guys are as big as the sun, body structure of StarCraft Leviathans, sentient)

First things first, anything that big will likely become a Sun. That is to say it is unavoidable that gravitational forces will result in it becoming a more compact body. If there is enough mass it will result in fusion taking place in the core. The physics for this (and you wanted a reality check) is absolutely unavoidable.

So they can't exist.

Note that the leap from these Leviathan's (about $7$ km in size) to something Sun sized (a little short of $700,000$ km in radius) is vast. An object 7km in radius which was hollow with a shell $0.5$ km thick made of something the density of water would have a mass of about $2.9\times 10^{14}$ kg. An object as large as the Sun with a similar shell would have a mass of about $3\times 10^{24}$ kg, which is about half the mass of the Earth ! And that's for an empty (!) entity as you describe it. It would end up as a planet - there's no practical way around this.

Now, the aliens have discovered machine augmentation. They lack limbs, but instead use long tentacles as graspers.

Interacting with other objects when you're planet size or larger in mass means they collide with you with enormous force - you have a gravitational field that attracts objects.

So what this object will have is lots of craters, like our moon (and the Earth would have them if it didn't have weathering and geological activity that smooths out the wrinkles over times).

Without a home, humanity takes it upon itself to do the impossible: colonise the bodies of the beasts themselves.

Well they'll be planets, so that seems quite reasonable.

It also means that on approaching an Earth sized body the two large masses will start accelerating towards one another and the collision will be enormous and destroy both (in the sense of creating enough heat to melt both and they would reform as one or more bodies).

They suck material from heavenly bodies through a toothless mouth,

You cannot suck something in a vacuum. There's nothing to suck. You can't create an inflow of gases by sucking which would drag other things with it.

and their stomach functions as a mass-energy reactor, with the aid of a particle-accelerator type environment,

Particle accelerators are enormous power drains - they could not be used to generate more power than they consume.

A mass-energy reactor is just buzz-words. It's meaningless.

If you mean they convert mass to energy, then that's fission or fusion.

where they collide the particles and utilise the Hawking radiation to power themselves.

You clearly don't know what Hawking radiation is (more buzz words being slapped together). It's a very small and very theoretical radiation expected in the region of black holes. It's not going to happen in any other circumstances and it requires an enormous gravitational field to power it. It's not possible to use Hawking radiation in any way you're suggesting.

The plan of the protagonists is to enter using special drop pods along with the material, latch onto the oesophagus wall, burrow into the muscle and deploy a colony there. The damage will be smalller than a pinprick for the giants, and they won't even notice. However, the immune system will.

All of this makes no sense.

An immune system would not react to anything unless it did something to activate it. Just being present is not enough. Humans could, in fact, probably live on the surface of your planet mass object. Going inside is pointless.

So, my question, what kind of punches would the immune system, biological or semi-mechanical, have to pack to present an actual threat to the human drop pods or the people themselves?

The entity could safely ignore the humans and they could exist together without issue.

The aliens do generate their own gravitational field.

Unavoidable with the mass of a planet or star.

Humanity's technological level is sufficient to allow interplanetary travel.

Which begs the question why are we staying near this planet killer ?

More to the point, if you can travel between stars it beggars the imagination you couldn't have just fired an extremely high kinetic energy lump of matter at the planet killer in the first place. At minimum a deterrent, at best enough to do it serious damage.

The immune system cells of the giants are likely to be bigger than the people or their drop pods.

Even if I accept the need for such things (which I don't) they are grenade fodder. A non problem.

The humans are carrying a military force, including heavy artillery, armored vehicles, and troop transports

Precisely what these idiots could do against a planet sized mass is beyond me. Every nuke on Earth would do no damage at all in any practical sense to something as large as you describe. I would describe them as wasted effort. There's no need or purpose in entering the body of the planet killer at all and there's no need to worry about an immune system that won't care what these things do.

• Excellent use of a counterargument for reality check. – Frostfyre Mar 1 '18 at 13:26
• I like this answer. Small correction: there was no mention of interstellar travelling capability, only interplanetary travel. – Real Subtle Mar 1 '18 at 14:34
• With regard to his mention of mass-energy conversion, hawking radiation, and particle-accelerators. Perhaps he meant something like a Kugelblitz reactor? – Shufflepants Mar 1 '18 at 18:49
• Actually, space is not a true vacuum. It's just REALLY rarefied. But anyway, they can just latch onto something they want to suck. Also, it is very likely that an object of this size can have an exoskeleton capable of supporting its size. After all, Starcraft leviathans are moon-sized. – Budhaditya Ghosh Mar 2 '18 at 17:22
• And yes, I was thinking of a Kugelblitz reactor. The amount of energy required to smash the protons together could easily be derived from the kinetic energy of such a giant thing moving through space. – Budhaditya Ghosh Mar 2 '18 at 17:24

Whatever the immune system of these giant creatures will be, if the human colonists are fighting them with conventional weaponry they won't have any relation to known biological immune system mechanisms. Our immune system largely works through several specialized cell types that perform tasks such as identifying, locating, and eating unwanted substances; but these are just cells. An individual biological cell is, essentially, a tiny soap bubble powered by amino acid strings; they just can't scale up too far and remain useful. There are single-celled organisms that are big enough to see (e.g., slime molds, and apparently the unicelluar plant caulerpa taxifolia, which can get up to six inches long (https://www.sciencedaily.com/releases/2015/01/150129160728.htm).) But these are sessile- the mechanisms that let bacteria or T-cells move around just aren't powerful enough to budge something that large.

The idea of a giant organism having some kind of innate internal defenses against human-sized "diseases" is viable- certainly not weirder than the rest of your scenario, which I think could be saved if you consider StephanG's points and adjust accordingly. But stellar-body-sized creatures are already so weird that you have more or less free hand designing what that immune system "cells" would be like. Are they swarms of robot bees? Giant eyes that spit acid? Maybe they look exactly like humans in every respect? Do what works best for the story.

I am not a biologist, or especially interested in biology, so the claims I am going to make are based on knowledge which likely ranges from "vague" to "wildly incorrect". It "sounds okay" to me based on that knowledge, but since the knowledge itself is suspect my conclusions are even more so.

If we handwave the enormous complications of the premise brought up by StephenG, we can envision this action as basically an "infection" of the Leviathan by human "bacteria". Presumably this is a never-before-seen bacteria among the Leviathan species, so they wouldn't have taken a "Human Vaccine" to have any specialized or prepared immune response. Without knowing more about the species, especially its society, it's tough to say whether there would be any broadly-applicable medication that would be relevant, but either way that's more of a later concern; manual attempts to cure something don't come until symptoms do, and symptoms usually aren't noticeable before we would need to deal with at least the first immune response.

You mentioned in a comment that you expect the "defenders" to still be single cells, but I would expect otherwise. In fact, I would argue that multi-cellular organisms already exist as part of immune systems, in the form of Remora and more abstractly Pilot Fish. While these aren't substantially "inside" their host, their mutually beneficial arrangement has the fish protecting their host from skin parasites, easily moving around the portion of the body that they are useful for. At the same time, there is also precedent for internal organisms which are not genetically a part of their host, with humans having both various and numerous examples. Thus, I don't think it's any great stretch for a being of planet-eating size to have internal colonies of multi-cellular organisms dedicated to expelling foreign threats.

In fact, I would imagine the situation as very similar to the humans finding themselves suddenly a part of any substantially unfamiliar ecosystem with little prior knowledge or time for preparation. The "locals" could be shaped in whatever way, use natural or artificial weapons, be intelligent and individual or mindless drones... Just about anything is possible.

If you want them to be a threat against a human army, then their typical threats need to be at least similar in scale. It's not unreasonable that "natives of the food get uppity" is an everyday occurrence to Leviathans and the immune response is very prepared for attacks of that nature. On the other hand, maybe humans are an unusually cohesive assault where prior experiences were mostly dealing with dispersed stragglers; the immune system has weapons effective against humans and even our heavier equipment, but wasn't prepared to deploy them in threatening numbers and the humans can establish a foothold. Potentially, they could even be completely unprepared for fighting this sort of threat and humans have a chance for a decisive pre-emptive strike... Or a truce! There's even room for tension among the humans between the ones that are willing to enter a peaceful niche and the ones that want conquest or revenge, if you setup the world right that could be a more significant conflict than between the humans and the aliens.

To me, there is a lot of potential for this cataclysmic Leviathan to internally be an intricate ecosystem and even civilization in an interesting and enjoyable way, but I also think that limiting the immune system to single-cell organisms reduces that potential by a large factor.

• Good idea. Symbiotic organisms are intelligent. Thanks. – Budhaditya Ghosh Mar 2 '18 at 17:29

You can't assume that the immune system of these creatures will be similar to anything we'd call an immune system. Star-sized creatures must be at least as different from us as we are from single celled organisms. There may, in fact, be no system which is directly analogous to our immune system. But let's say there is. Why? Because handwavium operates at the speed of plot. It's nice to tell a story about giants that have human like features.

So what would our immune system look like, scaled up? How would it pack a punch?

We have two major branches of our immune system. We have the innate system and the adaptive system. The innate is older, and operates in very broad ways. It includes things like tears and mucus, which serve to sweep hazardous elements away from sensitive areas. Your humans will come across something similar as they try to pierce the esophagus. It wont be like cutting a hole in the wall. It will be like cutting a hole in a wall that is constantly oozing, dragging your cutting tools away from the sensitive surfaces.

This system also includes cells like macrophages, which have very rudimentary pattern matching capabilities. They recognize patterns that have been seen in the past on undesirable cells, but which never appear on hosts. These might pick up an element of the humans which they find offensive, or they might not. If they don't pick anything up, then these cells will literally ignore the humans. On the other hand, if they see a threat, they will consume it, and then begin chemically digesting it. You can imagine all sorts of nasty chemicals like hydroflouric acid being used to dismantle the humans.

Part of the innate system is fever. If enough infection is detected, the body will raise its temperature in an attempt to make it inhospitable to non-host cells.

The key to all of those innate systems is that they really don't know what they're fighting. They're making very broad strokes. The story is different for the adaptive system. The adaptive system would be completely silent at first, because it only strikes when it knows what it's up against. But it is ruthless. Once the adaptive system starts to think it understands what a human is, and that it's bad, it will unleash customized attacks tailored to hunt and kill humans. Have you ever heard of dimethyl mercury? Most haven't. It's not something you find in nature. In fact, it's not something you want to experience at all. It is incredibly toxic. 0.1mL is enough to kill you. And it tends to osmose rapidly through hands and latex gloves. The adaptive system may construct strange chemicals like this tailored to get through our clothes and skin and wreak havoc.

Of course, that's all chemical level fun. We are talking about a star sized creature, with enough handwavium to permit it not to just collapse into a plain ol' star. It's immune system is going to be exotic. The innate system is likely to be more interesting, but the adaptive system should be fascinating. It may be able to bring to bear fantastical creatures tailored for one thing: killing humans.

In fact, I would find it beautiful and ironic if the adaptive system constructs a host of human-like entities whose sole job is to reach out and destroy humans. This would permit them to use not only basic chemical warfare, but social warfare as well, dismantling team unity from the inside.

After all, we are the most dangerous game.

If an environment contains anything that can power a reaction which produces energy at conditions compatible with life, there will be a microbe to exploit it. There are bacteria which eat uranium and hydrogen peroxide, and even radiotrophic fungi powered by gamma rays. If you leave bacteria and antibiotics together for long enough they will probably find a way to use your antibiotics as food.

Therefore, your Leviathan is a host to tons of microbes which it picked up along the way of its stellar wanderings. Some of them will be beneficial, like the ones in our gut, some of them not. It needs an immune system on the same scale as the microbes, so you can forget all about the ten foot tall white blood cells.

In the past, it ate worlds which were home to various species, and they somehow found a way to hitch a ride. A symbiotic relationship developed.

When it is the humans' turn, and they board the Leviathan... they will meet quite a few aliens there already. Perhaps some of these aliens are even controlling the creature.

Convincing them to let the newcomers onboard would be an interesting challenge...