Darko Mrakovcic wrote:

>I suppose that similarity of the foreign proteins to the endogenous
>proteins has been generally recognized as the fundamental cause of some
>autoimmune reactions (in accordance with your assertion). Of course, the
>first naive interpretation of this could be that proteins from closely
>related species should be more more harmful (e.g. mammalian vs poultry-
>derived, animal-derived vs plant-derived etc). On the other hand, a high
>degree of similarity more likely means that the amino-acid sequence is
not
>perceived as foreign at all by the immune system (unless the very fact
>that a protein appears in the digestive tract is sufficient for its
>classification as foreign). I assume this issue has probably been
>completely resolved - does anyone know what the answer is?

A high degree of similarity is supposed to be how "molecular mimicry"
works.  The invading protein is similar to an native tissue protein,
but different enough to be identified as foreign.  Once the immune
system learns the identity of the invading protein, it thereafter also
mistakes the native tissue as foreign, and attacks it, causing
autoimmune disease.

This theory may well be the explanation for some autoimmune diseases.
If it is, though, I don't see how ceasing consumption of the original
invading protein would make much difference.  Once the immune system
has learned to attack a native tissue, I don't see how it unlearns it.

>The question of quantity of foreign proteins, raised in the Jim Swayze -
>Todd Moody debate in another thread, is obviously also relevant in this
>context. My guess would be that Jim's theory (that quantity counts) is
>more viable simply because a minute exposure to a viral agent will not
>AFAIK cause a virus-induced auto-immune disorder. I believe this
>controversy can be reduced to the question of whether e.g. severity of
>symptoms of coeliac disease is dependent on the dose of gluten. Does
>anyone have data on this?

No, but I know that even a very small amount of gluten is sufficient to
cause considerable distress.  My position is not that amounts make no
difference at all, but rather that the model that we're working with
suggests that even rather small amounts should be enough to trigger a
response.  For that reason, I am skeptical of Jim's position that
unrefined foreign protein sources would be significantly less likely to
cause problems.

Todd Moody
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