Circulating immune complexes induced by food proteins implicated in precocious myocardial infarction.

Circulating immune complexes (CIC) are frequently found in postinfarction patients. The constituents of these CIC are mostly unknown. The objective of the current study was to assess whether CIC containing alimentary proteins and antibodies against these proteins are implicated in precocious myocardial infarction (MI). Seventy-six survivors (67 men and 9 women, mean age 39 years) of a first MI before the age of 45 years were enrolled in this study. Two control groups were included. One group consisted of age-matched, randomly selected, population-based healthy individuals, 79 men and 11 women, without features of coronary heart disease. An additional control group was used only for the determination of serum antibodies against some of the alimentary proteins and consisted of 139 healthy blood donors, 95 men and 44 women, with a mean age of 42 years. Sucrose density gradient centrifugation, gel filtration and precipitation by polyethylene glycol were used for the isolation of CIC, and enzyme-linked immunosorbent assay (ELISA) was used to measure the immunoglobulin levels and specific antibodies against alimentary proteins in both sera and isolated CIC. Sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis and Western blotting were used to determine alimentary proteins in the CIC. Alimentary antigens/antibodies were present in immune complex form in seven out of 14 (50%) postinfarction patients who had persistent high concentrations of CIC, the latter constituting 18% of the entire group. Antibodies of the IgG isotype predominated. A rise in CIC, signs of activation of the classical complement pathway, and a rise in plasma concentrations of von Willebrand factor antigen (vWFAg) were evident within 1 week in four patients subjected to a 2-week elimination diet followed by a single challenge with cow's milk. This study suggests that dietary proteins occasionally give rise to persistent CIC, which may predispose to MI at a young age.