Development of quality control preparations for immunocytochemical assessment of urokinase-type plasminogen activator

Quality control of immunochemical and/or immunocytochemical analyses warrants constant reproducibility and reliability of assay performance. In this respect, stable reference preparations containing known quantities of the components to be assessed may serve purposes in the quality assessment of antigen expression levels, including those of the plasminogen activation system. Quality control preparations for the immunocytochemical assessment of urokinase-type plasminogen activator (uPA) were developed using different combinations of cultured cell lines (BLM and IF6), each expressing immunochemically well-defined (by enzyme-linked immunosorbent assay[ELISA]) amounts of the respective component. Cytospins and frozen sections cut from sucrose/Tissue-Tek blocks containing these cell lines demonstrated stable and homogeneous expression of uPA. An excellent correlation was found between the immunocytochemical staining results and the data obtained by ELISA. Because these cell lines are available in practically unlimited quantities, large numbers of nearly identical quality control preparations can be made over a long period of time. Therefore, the incorporation of (combinations of) cell lines in cytospins or sucrose/Tissue-Tek blocks represents a simple model system in establishing quality control preparations for immunocytochemical assessment of components of the plasminogen activator system.