Role of immunoglobulin G3 subclass in dilated cardiomyopathy: results from protein A immunoadsorption

Immunoadsorption (IA) by anti-immunoglobulin G (anti-IgG) columns that effectively eliminates total IgG, including IgG3 subclass, represents an additional therapeutic approach in dilated cardiomyopathy (DCM). A recent study revealed that IA with protein A columns does not effectively remove IgG3 and does not induce hemodynamic improvement in DCM.

Eighteen patients with DCM (left ventricular ejection fraction < or =30%) were included in this case-control study. In all patients, IA with protein A was performed in 4 courses, at 1-month intervals until month 3. Nine patients underwent protein A IA with an improved treatment regimen for IgG3 elimination. Data of these patients were compared retrospectively to existing findings for 9 comparable patients treated by protein A IA with ineffective IgG3 reduction.

In both groups, IA induced a comparable reduction of the total IgG level. However, reduction of the IgG3 level was different in the 2 groups (P < .001). Hemodynamics did not significantly change throughout the 3 months in the group with ineffective IgG3 reduction. In contrast, the group with improved IgG3 reduction demonstrated during the first IA course an increase in cardiac index from 2.2 +/- 0.1 to 2.8 +/- 0.2 L min(-1) m(-2) (P < .05). After 3 months before the last IA course, cardiac index was 2.2 +/- 0.1 L min(-1) m(-2) in the group with ineffective IgG3 elimination and 2.8 +/- 0.2 L min(-1) m(-2) in the group with improved IgG3 reduction (P < .01). In the group with ineffective IgG3 reduction, left ventricular ejection fraction increased after 3 months from 21.6 +/- 2% to 24.4 +/- 2% (NS), and from 24.3 +/- 2 to 34.7 +/- 4% in the group with improved IgG3 reduction (P < .05).

Autoantibodies belonging to IgG3 may play an important role in cardiac dysfunction of patients with DCM. Protein A IA in conjunction with an improved treatment regimen for IgG3 elimination induces hemodynamic benefit in patients suffering from DCM.