title: Low level CD20 expression on T cell malignancies.
abstract: Although initially thought to be a B lineage restricted antigen, low "density" or antibody binding capacity (ABC) CD20 has recently been detected on subset(s) of normal T lymphocytes (Hultin et al.: Cytometry 14:196-204, 1993). We report low ABC CD20 expression in three (two children, one adult) cases of T-acute lymphoblastic leukemia (T-ALL). CD20 and other pertinent antigens were detected using a direct dual color method with a Becton Dickinson FACScan flow cytometer and Simulset software. Only one cell population based on light scatter was noted in each case that immunophenotypically represented almost a pure population of malignant cells expressing T lymphocyte antigens (for example, CD7 98%, 92%, and 100%, respectively). A total of 95%, 87%, and 79% of the cells from the three cases expressed CD20 with an unusual low ABC compared to the customary "bright" CD20 expression on normal B lymphocytes. Other B lymphocyte associated antigens, such as CD19, CD22, Dr, and immunoglobulin light chains, were negative. Eleven other T lymphocytic malignancies from 1991 to 1993 were CD20 negative, including three other case of T-ALL (one adult and two children). One unusual case of intestinal small lymphocytic non-Hodgkin's lymphoma with a natural killer/T lymphocytic immunophenotype not described in this report appeared to be CD20"dim"+. Low ABC CD20 expression by T lymphocytic malignancies may provide a more unique immunophenotypic "fingerprint" to help support the diagnosis of T cell neoplasia vs. normal/reactive T cells (for example, low ABC CD20 cells represent only 2.4 +/- 1.5% of normal peripheral blood lymphocytes). This characteristic might also facilitate monitoring patients for residual or recurrent disease.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: West Michigan Flow Cytometry Service, Ferguson-Blodgett Hospital, Grand Rapids, MI 49503.
authors.forename: M J
authors.initials: MJ
authors.lastname: Warzynski
authors.forename: D M
authors.initials: DM
authors.lastname: Graham
authors.forename: R A
authors.initials: RA
authors.lastname: Axtell
authors.forename: M H
authors.initials: MH
authors.lastname: Zakem
authors.forename: R K
authors.initials: RK
authors.lastname: Rotman
mesh_terms: D000328:Adult; D015703:Antigens, CD / Q000032:analysis*; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D015459:Leukemia-Lymphoma, Adult T-Cell / Q000175:diagnosis / Q000276:immunology* / Q000473:pathology; D008297:Male; D012984:Software; D016176:T-Lymphocyte Subsets / Q000276:immunology* / Q000473:pathology
chemical_list: D015703:Antigens, CD; D018951:Antigens, CD20; D000944:Antigens, Differentiation, B-Lymphocyte