The proatherogenic properties of lipoprotein(a) may be enhanced through the formation of circulating immune complexes containing Chlamydia pneumoniae-specific IgG antibodies

Aims To investigate a possible relationship between the atherogenic properties of lipoprotein(a) (Lp(a)) and Chlamydia pneumoniae infections. Methods and Results The study population was nested within the Vasterbotten Intervention Program or the WHO MONICA project. In this incident case-control study, 78 patients who had suffered acute myocardial infarction and 156 matched controls were included. The contents of circulating immune complexes were analysed for C. pneumoniae IgG antibodies and Lp(a). A significantly larger proportion of cases than controls had greater than or equal to 13 mg.l(-1) Lp(a) and a C pneumoniae specific IgG antibody titre greater than or equal to 1/2 in circulating immune complexes (odds ratio=3.8). Conclusion The proatherogenic effects of Lp(a) may be enhanced and/or partly mediated through the formation of circulating immune complexes containing C. pneumoniae-specific IgG antibodies. The connection between chronic C. pneumoniae infections and atherosclerosis may, at least in part, be explained by an interaction with Lp(a) through the formation of circulating immune complexes. (Eur Heart J 2000; 21: 639-646) (C) 2000 The European Society of Cardiology.