Selective Expression of CD45 Isoforms Defines CALLA+ Monoclonal B-Lineage Cells in Peripheral Blood From Myeloma Patients as Late Stage B Cells

• Published in: Blood 1991-08, Vol.78 (3), p.711-719
• Main Authors: Jensen, Gitte S., Mant, Michael J., Belch, Andrew J., Berenson, James R., Ruether, Bernard A., Pilarski, Linda M.
• Format: Article
• Language: English
• Subjects: Antibodies, Monoclonal; Antigens, CD - analysis; Antigens, CD - genetics; Antigens, Differentiation - analysis; Antigens, Neoplasm - analysis; B-Lymphocytes - immunology; Biological and medical sciences; Fluorescent Antibody Technique; Hematologic and hematopoietic diseases; Histocompatibility Antigens - analysis; Histocompatibility Antigens - genetics; Humans; Immunoglobulin A - analysis; Immunoglobulin G - analysis; Leukocyte Common Antigens; Medical sciences; Multiple Myeloma - blood; Multiple Myeloma - immunology; Neprilysin; Paraproteinemias - blood; Paraproteinemias - immunology; Restriction Mapping
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V78.3.711.711

The peripheral blood lymphocytes from 42 patients with multiple myeloma (MM) and 13 patients with monoclonal gammopathy of undetermined significance (MGUS) were studied by three-color immunofluorescence (IF) using antibodies directed to a broad range of B-cell markers (CD19, CD20, CD21, CD24), CALLA (CD10), PCA-1 (a plasma cell marker), and to the high and low molecular weight isoforms of the leukocyte common antigen, CD45RA (p205/220) and CD45R0 (p180). CD45RA is expressed on pre-B and B cells, and a transition from CD45RA to CD45R0 defines differentiation towards plasma cells. Peripheral blood mononuclear cells (PBMC) from patients with myeloma included a large subset of B-lineage cells (mean of 39% to 45%) that were CALLA+ and PCA-1+ in all patients studied, including newly diagnosed patients and patients undergoing chemotherapy. Southern blot analysis indicated the presence of monoclonal Ig rearrangements in PBMC and a substantial reduction in the germ-line bands consistent with the presence of a large monoclonal B-cell subset. Avoidance of purification methods involving depletion of adherent cells was essential for detection of the abnormal B cells. Phenotypically, this abnormal B-cell population corresponded to late B or early pre-plasma cells (20% to 80% of PBMC), as defined by the concomitant expression of low densities of CD19 and CD20, moderate densities of CALLA and PCA-1, and strong expression of CD45R0 on all B cells, with weakly coexpressed CD45RA on a small proportion. Heterogeneity in the expression of CD45RA and CD45R0 within the abnormal B-cell population from any given patient suggested multiple differentiation stages. Abnormal B cells similar to those in MM were also detected in MGUS, although as a lower proportion of PBMC (26%). Abnormal B cells from patients with MGUS expressed predominantly the CD45R0 isoform, but had a lower proportion of CALLA* and PCA-1+ cells than were found on B cells from MM. This work indicates that the large subset of circulating monoclonal B lymphocytes from myeloma patients are at a late stage in B-cell differentiation, continuously progressing towards the plasma cell stage.