Cd20 (pan-B cell) antigen is expressed at a low level on a subpopulation of human T lymphocytes

Authors

  • Lance E. Hultin,

    1. Department of Medicine and Jonsson Comprehensive Cancer Center, UCLA School of Medicine, Los Angeles, CA 90024
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  • Mary Ann Hausner,

    1. Department of Medicine and Jonsson Comprehensive Cancer Center, UCLA School of Medicine, Los Angeles, CA 90024
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  • Patricia M. Hultin,

    1. Department of Medicine and Jonsson Comprehensive Cancer Center, UCLA School of Medicine, Los Angeles, CA 90024
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  • Janis V. Giorgi

    Corresponding author
    1. Department of Medicine and Jonsson Comprehensive Cancer Center, UCLA School of Medicine, Los Angeles, CA 90024
    • UCLA School of Medicine, Department of Medicine/CIC, 12-939 Factor Building, 10833 Le Conte Avenue, Los Angeles, CA 90024-1745
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  • This work was supported by AI-72631, AI-72656, and CA-16042

  • This manuscript uses the style proposed in Nature 325:660, 1987. Thus, CDX refers to the cell surface differentiation antigen, e.g., the CD20 molecule, that is defined by a cluster of monoclonal antibodies (mAb). CD20 mAb refers to the cluster of mAb used to define the molecule specified, e.g., CD20 mAb refers to the cluster that includes Leu16, B1. and 1F5.

Abstract

Despite the previous description of the leukocyte differentiation antigen CD20 as B cell restricted, the findings reported here indicate that a small subset of human T cells expresses low levels of CD20 or a cross-reacting antigen. Three different CD20 monoclonal antibodies (mAb), Leu16, B1, and 1F5, reacted with the T cell subset. B cells that expressed CD20 were CD20bright and constituted an average of 9.2 ± 3.3% of adult PBL. Meanwhile, T cells that expressed CD20 were CD20dim and represented 2.4 ± 1.5% of the PBL. This population may have been overlooked in previous studies due to the low level of CD20 expression per T cell and the small size of the subset in most individuals. Blocking studies indicated that CD20 mAb binding to CD3+ cells was due to the antigen-reactive regions of the CD20 antibodies and was not a result of Fc receptor binding, or non-specific fluorochrome or protein binding. The T cell nature of the CD20dim CD3+ cells was confirmed by the rapid rise in the intracellular calcium concentration ([Ca2+]i) of CD20dim cells observed following treatment with CD3 mAb but not following treatment with anti-human immunoglobulin (Ig). Extensive three-color immunophenotypic analyses indicated that CD20dim T cells were phenotypically heterogeneous and displayed a leukocyte differentiation profile that was slightly different than that of CD20 T cells. Thus, the CD20dim T cells were more likely than CD20 T cells to be γ/δ T cell antigen receptor positive (14% vs. 3.4%), CD8+ (57% vs. 33%), and CD45RO+ (82% vs. 51%); fewer were CD38+ (5% vs. 24%) or CD4+ (35% vs. 61%). Given that most differentiation antigens expressed on leukocytes participate in the functions of the cells that express them, it is possible that CD20 plays a role on the T cells on which it is expressed, although the function(s) of the CD20 molecule on T and B cells remains unknown. © 1993 Wiley-Liss, Inc.

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