Association between human serum IgM to <i>P. gingivalis</i> and MDA-LDL, and competitive binding with recombinant gingipain domains.

<p>Sera from 29 healthy adults were analyzed for IgM (A) and IgG (B) binding to Pg and MDA-LDL by chemiluminescence immunoassay. Associations between antibody levels were analyzed with Spearman rank correlation test. Human sera were pre-incubated with recombinant gingipain domains Rgp44, Rgp15–27, RgpCAT (C, D) in a competitive immunoassay detecting IgM binding to immobilized MDA-LDL. The ratio of serum IgM binding (B/B₀) to MDA-LDL with and without competitor (175 µg/ml) in 29 human serum samples (C) and dose-dependent competition assays of one sample (D). Reciprocal competition assay was performed to analyze human serum IgM binding to Pg antigen competed with MDA-LDL, nLDL and PC-BSA in a representative sample (E). RU, relative units.