title: CD20 (pan-B cell) antigen is expressed at a low level on a subpopulation of human T lymphocytes.
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 gamma/delta 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%).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, UCLA School of Medicine, 90024.
authors.forename: L E
authors.initials: LE
authors.lastname: Hultin
authors.forename: M A
authors.initials: MA
authors.lastname: Hausner
authors.forename: P M
authors.initials: PM
authors.lastname: Hultin
authors.forename: J V
authors.initials: JV
authors.lastname: Giorgi
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D015703:Antigens, CD / Q000032:analysis*; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis*; D017252:CD3 Complex / Q000276:immunology; D002118:Calcium / Q000378:metabolism; D002469:Cell Separation; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D016130:Immunophenotyping; D008297:Male; D016176:T-Lymphocyte Subsets / Q000187:drug effects / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte; D017252:CD3 Complex; D002118:Calcium