calliecritturs
Posted : 10/1/2008 5:05:39 PM
"cause" isn't really the right word, and if a true "cause" were known they'd have it licked.
"trigger" is a better word -- in an immune-mediated or "auto-immune" disease (that's almost a misnomer -- 'auto-immune' is meaningless to many vet opinions so you see 'immune-mediated' most of the time now) something in the body triggers the body's own immune sytem to wage war on it's own body.
The immune system should go 'on' and 'off'. On when confronted with a disease or something it needs to protect against and 'off' when the threat is over. And the body actually 'records' when it forms anti-bodies against something in each cells' memory.
But then something causes the immune system to just plain not shut 'off' -- AND not just to stay in heightened awareness but also to simply perceive a threat when none is truly there.
Billy's body actually formed antibodies to a sick tick. We *know* he was exposed. We *know* his body actually formed antibodies as it should have to defeat the tick-borne illness.
BUT then the immune system didn't stop -- it then **generalized** and decided not JUST the red blood cells with disease were bad, and then red blood cells with antibodies were bad ... it just plain started killing ALL red blood cells -- not just in the blood in the veins/arteries but all the way back in the bone marrow where reticulocytes are formed (baby red blood cells).
THAT is just IMHA -- for some reason the body starts a war on something .. and then declares war not just on disease cells but on ALL cells of those types and THEN it can generalize further and **other** auto-immune or immune-mediated problems begin.
If you remember Outdoorschik's "Snickers" -- Snickers had IMHA and the steroids got the body to stop attacking the red blood cells but THEN altho it kept holding off on the rbc attack it started attacking platelets TOO. And that was ultimately what happened with Snickers -- not one but two immune-mediated reactions and somewhere she bled internally (and they don't know from what or where).
No one knows the 'cause'. Why the immune sytem generalizes or mis-fires like that. Not yet. But 'triggers'? That's where vaccines come in -- because they are so strongly involved in that immune system on/off thing and producing antibodies that the body is supposed to recognize as 'ok' -- this is why dogs who have had ANY sort of auto-immune problem are NEVER supposed to be vaccinated ever ever again -- because any vax can trigger more reaction.
Other things can trigger it too but they aren't as easy to identify ... (like ProHeart 6 -- a chemical -- they know it was involved but not exactly how).
Does that make sense?? It's a Callie-explanation but it's as good as I've been able to assimilate.