AGGREGATED HUMAN-IMMUNOGLOBULINS BIND TO MODIFIED PROTEINS

Human immunoglobulins treated at 55-degrees-C in vitro are able to int eract with maleylated bovine serum albumin (mBSA), but not with unmodi fied BSA. Gel filtration experiments demonstrated that the mBSA bindin g is associated with a high molecular weight complex of aggregated IgG . This aggregated IgG with binding capacity for mBSA could also be gen erated in vitro by treatment of human IgG at 37-degrees-C or 40-degree s-C and by incubation with human neutrophils. Furthermore, IgG aggrega tes with binding activity for mBSA could be detected in untreated syno vial fluids from rheumatoid arthritis patients, indicating that these complexes occur in vivo. The phenomenon of binding to aggregated IgG w as extended to other modified proteins such as maleylated human serum albumin (mHSA), acetyl low density lipoprotein (Ac-LDL) and BSA reacte d with oxidized linolenic acid. Soluble forms of these modified protei ns were able to compete for the interaction between aggregated IgG and surface-bound mBSA. We also found that aggregated IgG enhanced the Ac -LDL-dependent foam cell formation. These findings suggest a role for aggregated IgG in the metabolism of oxidized proteins.