Sunday, November 2, 2008

Can someone explain this genetic link?

Not the missing link... the genetic link that predisposes someone to Celiac Disease.

And just for the record, I had to actually do some research before writing this. Eeek! But that's ok, I've learned my one new thing for today.

So here's what I know so far: I have double copies of the HLA DQA1*05-DQB1*0201 gene. To those of you who know what that means, I am totally impressed. To those who don't, it means a lot. Mostly, that I carry two copies of the genes that put someone at risk for Celiac Disease (thanks Mom and Dad!) and am therefore at a 31x higher risk than the general population.

Translation please! Ok... so HLA stands for Human Leukocyte Antigens. These antigens are found on the surface of pretty much every cell in the body, but particularly on lymphocytes, which are the white blood cells of the immune system. HLA antigens do a very important work- they roam through the immune system and determine if other cells are "self" or "nonself". They are found on inflammatory cells throughout the lining of the intestine as a part of its constant seek and find.

Since we have two parents, we inherit two slightly different versions of these proteins. And they determine what sort of reaction we have to different foreign substances. So enter the Celiac/genetic link. These antigens are also believed to be a part in the development of genetically predisposed diseases, such as diabetes, and my good friend Celiac Disease.

Which brings up back around to the DQ genes. They encode particular HLA proteins that are on the cell surface. These genes are referred to as HLA-DQ2 or HLA-DQ8. The DQ2 or DQ8 proteins on the surface of lymphocytes have a groove that interacts with and binds to the gliadin fragment (the toxic portion of gluten). So to put it very simply, the immune cells are genetically geared to react to gluten.

The interesting part of this all is that somewhere around 30% of the population carries the genes. But not all of these people will have Celiac, they're merely predisposed. It's amazing what the study of genetics has taught us.

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