Immunoglobulins and complement in chronic myocardial disease. A myocardial biopsy study.

Autoimmune mechanisms have been suggested to be of significance in chronic myocardial diseases. However, the frequency and importance of these factors are unknown. In the present study, endomyocardial biopsy specimens from 21 patients with chronic myocardial disease have been examined by direct immunofluorescence for the presence of immunoglobulins and complement factor C3. Positive staining for immunoglobulin and/or complement was observed in 7 cases. None of the specimens stained for albumin or amyloid. The immunoglobulin deposits were located on the surface of the myofibre and in all but one case, complement was found in the same location. The presence of the complement together with immunoglobulin, and also the lack of albumin, may suggest an immune reaction and not just a passive deposition secondary to heart muscle damage. The localization along the fibres further suggests that the deposits represent an autoimmune reaction to antigens on the fibres and not a trapping of circulating antigen-antibody complexes. It is not known whether the deposits are primary or secondary events, but they may be of importance in initiating or maintaining derangement in heart function.