Combined method of PAP immunocytochemistry and autoradiography: application to cell kinetic study in plasma cell...

The plasma cell labeling index (LI), in spite of being a reliable indicator for diagnosis and prognosis of multiple myeloma, has been measured in a limited number of laboratories because of technical difficulties. We have developed a new combined technique, using the peroxidase-antiperoxidase (PAP) method and autoradiography, which has several advantages over previously described methods. The primary advantages of our method in the determination of lymphoid-plasma cell LI% are: (a) no damage to slides during storage of more than 1 year; (b) an exact LI measurement in each morphological variety of pleomorphic immunoglobulin-containing cells; (c) no problem in differentiation of lymphoid plasma cells from early red cell precursors; and (d) a separate LI measurement for those lymphoid-plasma cells composed chiefly, if not exclusively, of monoclonal or neoplastic cells. Because of these advantages, this accurate and less difficult technique will facilitate performance of lymphoid plasma cell LI in a number of laboratories.