Impact of CD138 Magnetic Bead-based Positive Selection on Bone Marrow Plasma Cell Surface Markers

CD138 magnetic sorting impacts the phenotypic characteristics of myeloma plasma cells. In our evaluation of bone marrow aspirates from 16 patients, we observed complete loss or under expression of cell surface antigens by CD138-positive sorting as compared with whole bone marrow lyse and wash method. This should be kept in mind when designing studies for diagnosis and treatment of multiple myeloma. Background: Isolation of malignant plasma cells from bone marrow of patients with monoclonal gammopathies is critical for studies into the disease biology. The plasma cells are typically isolated by positive selection using plasma cell markers such as CD138. Here we have examined the effect of CD138 magnetic bead selection on the expression of other surface phenotypic markers on plasma cells. Materials and Methods: Bone marrow aspirates from 16 patients were split and prepared using 2 methods before staining for flow cytometric evaluation. The first method (whole bone marrow) used an ammonium-chloride-potassium lyse of whole bone marrow followed by 2 phosphate buffered saline washes. The second method used CD138-positive magnetic sorting technology (Stem Cell Technology). The cells were run on the FACSCanto flow cytometer after staining for CD38, CD45, CD56, activation markers CD71, CD69, CD154, adhesion markers CD49d, CD49e, CD11a, CD11b, and CD66, B cell markers CD19 and CD20, and for clonality. Results: There was a substantial loss in the expression of CD71, CD11b, CD11a, CD69, and CD49e on plasma cells following CD138-based sorting. Moreover, in 8 of the 16 cases, there was a nearly complete loss of the CD45-positive subset with a loss of discrimination between CD45-negative and CD45-positive plasma cell subsets in the remaining CD138-sorted preparations. Conclusions: The change in immunophenotype of the plasma cells on magnetic sorting should be kept in mind when isolating plasma cells using CD138-positive selection for analysis of plasma cells. The technique for characterizing plasma cells should be selected based on the study design to prevent loss of crucial and valuable information. (C) 2020 Elsevier Inc. All rights reserved.

Automated summary

CD138 magnetic sorting impacts the phenotypic characteristics of myeloma plasma cells by leading to a substantial loss in the expression of certain surface markers, such as CD71, CD11b, as well as nearly complete loss of the CD45-positive subset in some cases. Researchers should be aware of these changes when using CD138-positive selection for analysis of plasma cells to prevent loss of valuable information.