Opacity-associated (Opa) proteins are outer membrane proteins which play a critical role in the adhesion of patho-genicNeisseriaspp. to epithelial and endothelial cells and polymorphonuclear neutrophils. The adherence is mainly mediated by the CD66-epitope-containing members of the carcinoembryonic-antigen family of human cell-adhesion molecules (CEACAM). For the analysis of the specific in-teractions of individual Opa proteins with their receptors, pure protein is needed in its native conformation. .
