Inability of Monoclonal Anti-light Chain Antibody to Detect Clonal B-Cells in a Patient with Follicular Lymphoma by Multicolor Flow Cytometry

Background Our recent publication “Inability of a monoclonal anti‐light chain antibody to detect clonal plasma cells in a patient with multiple myeloma by multicolor flow cytometry,” underlined the importance of choice of antibodies to detect cytoplasmic light chains. Our present study extends this finding for detection of surface immunoglobulin (SIg) light chains on clonal B‐cells. Methods Multicolor flow cytometry was used for analyzing bone marrow (BM) from a patient with a CD10‐positive follicular lymphoma for infiltrating clonal B‐cells. Results In the BM aspirate, B cells could be identified expressing CD19, CD10, and high levels of CD20. No SIg light chain expression was found on this population of B cells employing monoclonal antibodies. Re‐analysis using polyclonal antibodies against SIg light chains, revealed presence of lambda light chains on the CD10positive B‐cells. Conclusions These data illustrate when antibodies against SIg light chains are employed for B‐cell clonality assessment, polyclonal antibodies are preferred over monoclonal antibodies.