Potential Role of Autoantibodies Belonging to the Immunoglobulin G-3 Subclass in Cardiac Dysfunction Among Patients With Dilated Cardiomyopathy
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Background— Immunoadsorption capable of removing circulating autoantibodies represents an additional therapeutic approach in dilated cardiomyopathy (DCM). The role played by autoantibodies belonging to the immunoglobulin (Ig) subclass G-3 in cardiac dysfunction remains to be elucidated.
Methods and Results— Patients with DCM (left ventricular ejection fraction <30%) participated in this case-control study. Nine patients underwent immunoadsorption with protein A (low affinity to IgG-3), and 9 patients were treated with anti-IgG, which removes all IgG subclasses. Immunoadsorption was performed in 4 courses at 1-month intervals until month 3. In the 2 groups, immunoadsorption induced comparable reduction of total IgG (>80%). IgG-3 was effectively eliminated only by anti-IgG adsorption (eg, during the first immunoadsorption course; protein A, −37±4%; anti-IgG, −89±3%; P<0.001 versus protein A). The β1-receptor autoantibody was effectively reduced only by anti-IgG (P<0.01 versus protein A). Hemodynamics did not change in the protein A group. In the anti-IgG group during the first immunoadsorption course, cardiac index increased from 2.3±0.1 to 3.0±0.1 L · min−1 · m−2 (P<0.01 versus protein A). After 3 months, before the last immunoadsorption course, cardiac index was 2.2±0.1 L · min−1 · m−2 in the protein A group and 3.0±0.2 L · min−1 · m−2 in the anti-IgG group (P<0.01 versus protein A). Left ventricular ejection fraction increased only in the anti-IgG group (P<0.05 versus protein A).
Conclusions— Autoantibodies belonging to IgG-3 may play an important role in cardiac dysfunction of DCM. The removal of antibodies of the IgG-3 subclass may represent an essential mechanism of immunoadsorption in DCM.
Received April 17, 2002; revision received August 23, 2002; accepted August 24, 2002.