AUTOIMMUNE DISEASES

Debbie Martin: When we look at some of the diseases that our dogs have, like autoimmune hemolytic anemia, allergies, cancers, inflammatory-bowel diseases, we keep hearing a description of the immune system attacking cells, attacking red blood cells, attacking new growth in the bone, attacking pollen, attacking everything. In your opinion, are these linked somehow?

Dr. Padgett: Autoimmune diseases as a whole are linked. For example: Rheumatoid Arthritis, Lupus, Autoimmune Hemolytic Anemia, and a platelet disorder (Autoimmune Thrombocytopenia). There is a link between that set of diseases. There’s no doubt. And we don’t have a mode of inheritance in any species in those diseases, even though we know they’re inherited. It might be that we just can’t count right. You know, because we don’t know what diseases to include.

When we look at them separately we can’t come up with a mode of inheritance for those traits. It just doesn’t work out. We know that families with autoimmune diseases are more likely to show up with other autoimmune diseases. They occur within families more often than they do in families that don’t have them, and it’s not always the same disease that shows up. In one case you’ll have lupus, and then a brother or sister will have autoimmune hemolytic anemia, not lupus. They don’t act like we would typically expect a genetic disease to do.

Whether that extends into the cancers or not is not clear. I don’t have any data that says that that happens. Although, it might. You can’t rule it out either.

Others’ Questions: Are you saying there that you don’t have data that shows that cancer is related to immune system or immune disorders?

Dr. Padgett: To a specific disorder, immune disorder.

Others’ Questions: So whatever it is that allows an autoimmune disease to be prevalent in a family isn’t going to be the same affect as what allows cancer to be prevalent in another family?

Dr. Padgett: That’s right. That is what I would expect. I can’t give you data on that, but that is exactly what I would expect. I would expect the autoimmune system and autoimmune disorders to be different from that influencing the cancers.

Debbie Martin: When we’re trying to breed to avoid them, let’s say we’ve had different expressions of autoimmune disease, do we count them all as the same thing? Or do we breed just to exclude one version of it?

Dr. Padgett: I don’t think you can breed to avoid just one. We know they’re interrelated, and we know that when you breed one you get another one, a different one. And how exactly that works we can’t tell you. Where there’s one gene that can go two or three different ways, affects the cell, stem cells sometimes which goes two or three different directions we can’t tell you. But they are interrelated and I would look at them as one trait.

Others’ Questions: Have they been determined to be recessive or polygenic?

Dr. Padgett: They think Addison’s will turn out to be recessive, but the data’s not available yet. It’s not been published as such. Autoimmune Thyroiditis is a single gene trait.

Dale Malony: So we treat autoimmune disorders as a recessive not a polygenic?

Dr. Padgett: No. Not the other group. The only one we know for sure is recessive is autoimmune Thyroiditis.

Dale Malony: But for lack of anything better, if we want and try and use it in the selection process, then maybe it would be a good thing to use recessive probabilities versus polygenic?

Dr. Padgett: No. I think I’d use polygenic, but basically they’re exactly the same. With the polygenic trait you give minimum risk not maximum risk, because you have more genes involved and you calculate for one gene. And so the risk is that when you’re dealing with a polygenic trait, you must say that the risk is at least this and might be higher. But we can’t tell.