Homogeneous immunoassay for alpha 2 plasmin inhibitor (alpha 2PI) and alpha 2PI-plasmin complex. Application of a sandwich liposome immune lysis assay (LILA) technique.

The measurement of the alpha 2 plasmin inhibitor (alpha 2PI) and alpha 2PI-plasmin complex is important for a complete understanding of fibrinolytic conditions. Using monoclonal antibodies against alpha 2PI, a sandwich liposome immune lysis assay (LILA) has been used for the quantitation of alpha 2PI and the alpha 2PI-plasmin complex. In the assay system for the measurement of alpha 2PI, anti-alpha 2PI monoclonal antibodies were covalently coupled to liposomes and specific lysis of liposomes was observed when the liposomes were incubated with the alpha 2PI antigen, TNP haptenized second monoclonal antibody against alpha 2PI and complement activating rabbit anti-TNP antibody. The same liposomes and rabbit anti-plasminogen antibody could be used for the homogeneous determination of the alpha 2PI-plasmin complex. The former assay suggests that monoclonal antibodies lacking complement-activating ability can be used in the sandwich LILA technique. The second application suggests that the LILA technique is capable of measuring heterocomplexes. These assays, which involve the same analytical system, are simple, fast and highly sensitive. They are potentially useful in determining the fibrinolytic status of patients.