Immunohistochemical localization of modified C-reactive protein antigen in normal vascular tissue

Background: The prototypic acute phase reactant, C-reactive protein (CRP), is a serum soluble, cyclic pentameric protein, the concentration of which increases markedly with in hours of any tissue-damaging, inflammatory event. However, upon dissociation of its pentameric quaternary structure, CRP subunits undergo a spontaneous and irreversible conformational change. The resulting molecule, termed modified CRP or mCRP, has reduced aqueous solubility and a propensity to aggregate into a matrix-like lattice structure. Methods: Using monoclonal antibodies, normal human tissues were immunohistochemically screened for the presence of CRP as well as mCRP antigens. Results: Significant levels of mCRP were detected in the walls of blood vessels associated with normal human tissues. These data indicate that mCRP is a naturally occurring form of CRP and that it is a tissue-based rather than serum-based molecule. Significance: This report describes the localization of a stable form of CRP, mCRP, in blood vessels associated with normal human tissues.