Periodontitis and Inflammation: Plasma High Titer Naturally Occurring Anti-Glucan Antibodies Form Immune Complex with Streptococcus mutans Antigens

Atheromatous plaques usually contain antigens of the periodontitis-causing bacteria Streptococcus mutans though molecular mechanism of this incorporation remains unknown. Since vascular adhesion and inflammatory potential of Immune Complexes (IC) are known we investigated the naturally occurring plasma antibodies that recognize major antigens from S. mutans. S. mutansbinding plasma proteins (SMBP) prepared by affinity chromatography on a column of heat-killed S. mutans could recognize αand β-linked glucose in dextran and yeast respectively but not galactose in glycoproteins. SMBP contained only three proteins, each corresponding in electrophoretic mobility to standard plasma IgG, IgA or IgM. The major positively and negatively charged protein antigens (PSMAg and NSMAg) isolated from S. mutans by electrophoresis and ion exchange chromatography respectively were recognized sugar-reversibly by the anti-β-glucan antibody (ABG) and though less avidly, by the dextran-binding immunoglobulin (DIg) in normal plasma. NSMAg addition resulted in near doubling of IC-bound immunoglobulins in immunoglobulin-rich fraction of plasma. IC isolated from above fraction after NSMAg addition had substantially more IgA and IgM content than total plasma immunoglobulins. IC formation by NSMAg was significantly inhibited by ABGand DIg-specific sugars or by selective withdrawal of ABG or DIg from plasma. ABG and DIg being relatively high titer plasma antibodies IC formation with them suggested a possible route for Corresponding author.