Variable immunoreactivity of D-dimer preparations for monoclonal antibody DD-3B6/22

The monoclonal antibody DD-3B6/22, which is specific for crosslinked fibrin breakdown products, is used clinically in the diagnosis and monitoring of certain thrombotic conditions and has potential as a delivery agent for in vivo clot localisation. Laboratory preparations of D-dimer are used as reference standards in DD-3B6/22 assay systems. In this study, four D-dimer preparations, produced using a standardised method, were presented to the monoclonal antibody, DD-3B6/22 in different antigenic formats and immunoreactivity was assessed using a variety of methods. The results show a variability in reactivity of the D-dimer samples to DD-3B6/22; one preparation (QUT2) was immunoreactive only when immobilised on a surface and not when in solution. The implications of variable immunorecognition of target antigens are discussed with regard to diagnostic standards and in vivo clot localisation.