ScienceDaily (Jan. 20, 2005) — The immune system uses antibodies to target foreign, "non-self" proteins and cells. Autoimmune antibodies, by contrast, attack the body's own cells, and those circulating in women with lupus and other autoimmune diseases can also cross the placenta and cause congenital heart block in the fetus. Scientists in Sweden now show how these antibodies cause heart cells to become paralyzed and eventually die, according to a study in the January 3rd issue of The Journal of Experimental Medicine.

Autoantibodies had been implicated as a cause of congenital heart block in the past, but nobody knew how they were working. This study shows that the antibodies bind to heart cells and disrupt the proper fluctuations of calcium ions that allow the cell to contract, causing a toxic build up of calcium which triggers the death of the cell.

It is not known what protein on the cell surface these antibodies are binding to, nor is it clear how these antibodies are disrupting the calcium fluctuations that are required for the heart cells to contract. The authors are actively searching for the binding target of these antibodies. Meanwhile, they hope that their success in narrowing down the identity of the responsible antibodies will provide a new way to identify women who are most at risk for having children with congenital heart block.

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