Determination of the plasma cell labelling index with bromodeoxyuridine in a double fluorescence technique.

A new technique is described in which plasma cells actively synthesizing DNA can be identified in a heterogeneous cell population such as bone marrow. This method uses bromodeoxyuridine (BrdU) and a fluorescent monoclonal antibody against BrdU in combination with cytoplasmic staining for immunoglobulin (Ig). In 26 patients with monoclonal gammopathy (MG) the plasma cell labelling index (LI) as determined by this immunofluorescent method was compared with the tritiated thymidine (3H-TdR) LI. No difference in sensitivity was found between the two methods. As the determination of the plasma cell LI with the BrdU/anti BrdU method is easy to perform and results can be obtained within 4 h, this immunofluorescent method seems to be an attractive alternative to the laborious time-consuming classic 3H-TdR LI.