Detection of immunoglobulin light-chain mRNA in lymphoid tissues using a practical in situ hybridization method

The identification of immunoglobulin protein in routinely fixed and paraffin-embedded sections using antibodies combined with immunoperoxidase or similar techniques of detection is often problematic. We developed an in situ hybridization methodology for the identification of light-chain mRNA that is applicable to formalin-fixed, paraffin-embedded tissues, using either radiolabeled or biotinylated oligonucleotide probes based on the kappa and lambda light-chain gene-constant regions. Reactive plasma cells can be consistently identified in reactive lymphoid tissues, and a monotypic pattern of light-chain mRNA restriction was seen in each of eight cases of multiple myeloma/plasmacytoma. Immunoblasts and germinal center cells also are labeled in reactive lymphoid tissues. Using 355-labeled probes, 29 of 93 cases (30%) of non-Hodgkin's lymphomas had detectable light-chain mRNA, while 19% of non-Hodgkin's lymphomas were positive using biotinylated probes.