Interaction between humans and organisms that evolved separately.

[Zurr]

Okay, to be honest here, the title doesn't really do the actual question justice. For that, I need to add some backstory.

 

I am not very good with studying in the traditional sense(never picked it up and I suffered for it) so the way I would learn things is to put them in a context interesting ienough for them to be retained. As such, I learn most things by imagining what would happen in custom-built scenarios.

 

In this particular case, I was trying to figure out how humans would react to life on another planet. More specifically, what would happen if the native life on the planet had (for whatever reason) originated in a way that caused it to be built of protiens, but otherwise completely alien.

 

Taking it step by step, the first thing (throwing how the life originated out the window) was how unucellular organism that behave much like earth microbes (i.e protien digesting bacteria) would interact with humans. From my understanding, the reason external and internal microbes don't cause us to decompose is because our immune system stops them from doing so. However, there are microbes which our immune system cannot handle whice give us diseases.

 

What I want to ask first, is: is it necessary for our immune system to prepare a specific antibody for every kind of intruder? Are there general purpose antibodies that destroy a wide range of different disease vectors?

 

I realise the question may be vague, and perhaps not even useful. It could be that the type of microbe that exists in the alien life form being affected/not affected by our immune system is totally arbitrary and dependent on how similar or different the alien is from standard earth life. Still, any answer could serve to at least give me a little idea on what kinds of questions I should ask instead.

[Acme]

...

What I want to ask first, is: is it necessary for our immune system to prepare a specific antibody for every kind of intruder? Are there general purpose antibodies that destroy a wide range of different disease vectors?...

No; antibodies aren't necessary for the immune system to destroy 'intruders'. I'm no expert and it's rather a complex family of defenders, but you might get started by reading up on phagocytes.

 

Wiki is as good a starting place as any, but if you don't like that then just do a web search for 'phagocyte' and pick your poison.

Phagocyte @ Wiki

Phagocytes are cells that protect the body by ingesting (phagocytosing) harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek phagein, "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek kutos, "hollow vessel".[1] They are essential for fighting infections and for subsequent immunity.[2] Phagocytes are important throughout the animal kingdom[3] and are highly developed within vertebrates ...

[Zurr]

No; antibodies aren't necessary for the immune system to destroy 'intruders'. I'm no expert and it's rather a complex family of defenders, but you might get started by reading up on phagocytes.

 

Wiki is as good a starting place as any, but if you don't like that then just do a web search for 'phagocyte' and pick your poison.

Phagocyte @ Wiki

 

Thanks for the answer.

 

From what I've read, would it be correct to assume that, generally, if there is an organism that does not know what a human is, it would not have evolved any specific mechanism for escaping phagocytosis? If that is the case, then the human immune system is able to identify 'intruders' in general, and destroy them if they don't have a way to avoid phagocytes. Which would mean that the vast majority of disease due to cellular infection occurs because the disease-causing cells have specifically evolved a way to cause that disease.

 

Is that right?

[Acme]

Thanks for the answer.

My pleasure.

 

From what I've read, would it be correct to assume that, generally, if there is an organism that does not know what a human is, it would not have evolved any specific mechanism for escaping phagocytosis?

I'm not sure we can make such an assumption. Particularly in regards to extraterrestrial microbes.

 

If that is the case, then the human immune system is able to identify 'intruders' in general, and destroy them if they don't have a way to avoid phagocytes. Which would mean that the vast majority of disease due to cellular infection occurs because the disease-causing cells have specifically evolved a way to cause that disease.

 

Is that right?

Well, some phagocytes don't differentiate as to whether an intruder is a disease causing agent or simply foreign material. Then too, it is often a matter of numbers that determines if an intruder is successful or not. That is to say the intruder replicates faster than phagocytes can destroy them.

[Delta1212]

But generally, yes. Bacteria, viruses, and what have you generally evolve to specifically infect a particular host or set of hosts and crossover to something else is generally accidental and not terribly common.

 

It would likely take quite a long time and very consistent exposure to any bacteria-analogue on an alien world before a strain cropped up that was capable of infecting humans. It'd be a bit like give a tree a cold.

[Acme]

But generally, yes. Bacteria, viruses, and what have you generally evolve to specifically infect a particular host or set of hosts and crossover to something else is generally accidental and not terribly common.

 

It would likely take quite a long time and very consistent exposure to any bacteria-analogue on an alien world before a strain cropped up that was capable of infecting humans. It'd be a bit like give a tree a cold.

Someone made the no-crossover argument here recently in another thread. At least you qualified your statements with 'generally' and 'not terribly common'. Still, it happens and so it's not to be discounted even on an alien world. My answer to the argument in the other thread was Rabies. In that case it would be exactly like a dog giving a human Rabies in short order with a good bite.

[barfbag]

@ Zurr,

 

 

What I want to ask first, is: is it necessary for our immune system to prepare a specific antibody for every kind of intruder? Are there general purpose antibodies that destroy a wide range of different disease vectors?

 

 

http://en.wikipedia.org/wiki/White_blood_cell

 

(Is this what you are wanting to see?)

[Acme]

.

The transfer of diseases across species is called zoonosis. In humans it is not uncommon.

 

Zoonosis @ Wiki(Bolding mine.)

Zoonosis /ˌzoʊ.əˈnoʊsɨs/ (also spelled zoönosis; plural zoonoses) describes the process whereby an infectious disease is transmitted between species (sometimes by a vector) from animals other than humans to humans or from humans to other animals (the latter is sometimes called reverse zoonosis or anthroponosis). In direct zoonosis the agent needs only one host for completion of its life cycle, without a significant change during transmission.[1]

 

In a systematic review of 1,415 pathogens known to infect humans, 61% were zoonotic.[2] The emergence of a pathogen into a new host species is called disease invasion or "disease emergence".

 

The emerging interdisciplinary field of conservation medicine, which integrates human and veterinary medicine, and environmental sciences, is largely concerned with zoonoses.

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