Natural IgM class antibody and C-reactive protein (CRP) are phylogenetically old effector mechanisms of innate immune response. Under physiological circumstances, they are involved in the removal of apoptotic cells.
After invasion of the body by pathogenic bacteria, CRP and IgM class antibody mount the first line of defense removal the invading organisms from the circulation. In apoptotic cell membranes, in the cellular membranes of some pathogenic bacteria, and in modified lipoprotein particles, natural antibody and CRP recognize an identical biding ligand, which is the phosphorylcholine molecule.
In the body, choline phosphate is an antigen epitope becoming available as a result of oxidation of apoptotic cell membranes and LDL particles. Through the genetic predisposition of the body and the action of external factors, which can include some infectious diseases, this originally antiatherogenic reaction turns into a proatherogenic process.