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Comment by DoreenMichele | Hacker News Reader

But the reason for that death isn't clear, and the typical signs of rejection by the immune system weren't present.

Perhaps because it involved a pig heart, not a human heart? If this is new territory, I see no reason to expect failure to follow "typical" patterns.

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Transplantation of organs from animals into humans has been tried in the past. Because of that, we know what full on rejection of non-human organs looks like.

It sounds like this was actually quite successful in that the immune system didn’t immediately start attacking it, as would be the case with a normal pig heart.

That’s a great thought, however, when you look at tissue under a microscope you should see evidence that the immune system was at play. This means the presence of complement activation (an ancient arm of the immune system), antibodies, white blood cells, nuclear debris, and so on. Presumably when they saw no evidence of immune mediated rejection, they saw none of this.

My lay person understanding as someone with a condition where people get a lot of transplants is that we don't actually know what causes rejection.

Perhaps in some cases the organ contains unidentified infective agents, thus the typical pattern with white blood cells etc.

Perhaps in this case the body decided it was straight up foreign matter and the process of failure was fundamentally different.

Your point that this is uncharted territory is well-taken, we can't say for sure, but the above poster has it right. I do not know of any circumstance in medicine in which evidence of immune reaction against foreign material would be non-obvious. I'm a pathologist and this is my area of expertise.

To be clear, I have two points:

1. This is uncharted territory.

2. My understanding is we don't actually understand "normal" rejection all that well to begin with.

If we don't know how and why rejection occurs to begin with, we have no reasonable means to distinguish it from some other type of failure.

But I shall stop annoying professionals with my amateur opinions here.

Have a good day.

We may not know what causes rejection, but are pretty good at seeing the signs of it. Extreme example: if a house collapses, you may not know immediately why it collapsed, but all the debris on the ground is a pretty good sign it's not in one piece anymore.

Rejection leads to death.

The guy died.

Anyway, trying to walk away from this particular thread.

What kind of logic is that? Ok here:

"We don't see signs that this person was shot in the head"

DoreenMichele: Getting shot in the head leads to death. The guy died.

What if it's something like the human blood cells stop delivering oxygen and nutrients to those tissues for one reason or another?

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