Quintanilla-Martinez L, Preffer F, Rubin D, Ferry J A, Harris N L
Department of Pathology, Massachusetts General Hospital, Boston 02114.
Am J Clin Pathol. 1994 Oct;102(4):483-9. doi: 10.1093/ajcp/102.4.483.
CD20 is a 35-kDa protein that is expressed early in B-cell ontogeny and is lost during terminal B-cell differentiation into plasma cells. It is thought to be B-cell-specific. However, the CD20 antigen, detected by the monoclonal antibody L26, has been reported in some cases of T-cell lymphoma. This report describes a case of a malignant lymphoma coexpressing T-cell-lineage antigens and CD20 and characterization of a CD20+ T-cell population in the peripheral blood of healthy donors. The tumor cells were pleomorphic medium-sized cells that expressed a range of T-cell-specific antigens, including CD2, CD3, CD4, CD5, CD6, CD7, and beta F1. In addition, the tumor cells expressed CD20 on frozen (B1) and paraffin sections (L-26). Stains for other pan-B cell antigens, including CD19 and CD22, and immunoglobulin light and heavy chains were negative. To determine whether this unusual coexpression of T-cell-lineage antigens and CD20 represented aberrant antigen expression or neoplastic transformation of an unusual normal T-cell subset, the authors examined specimens of peripheral blood lymphocytes from healthy donors for evidence of a CD20+ T-cell population by using three-color immunofluorescence analysis by flow cytometry. Two distinct populations of CD20+ cells were observed in peripheral blood. One expressed bright CD20 (6.6% to 23.7%, mean 14.47% of peripheral blood lymphocytes) and other B-cell associated antigens, whereas the other expressed dim CD20 (.94% to 11.90%, mean 3.50% of peripheral blood lymphocytes) and coexpressed CD3. Approximately two thirds (52.8% to 82.3%, mean 64.1%) of the dim CD20 cells were CD8+ and one third (19.2% to 74.1%, mean 37.5) CD4+. These cells also expressed CD5 and the alpha-beta chain of the T-cell receptor and lacked CD19 and CD22. These results indicate that CD20 is expressed on some normal peripheral blood T cells. CD20 expression by T-cell lymphomas may represent neoplastic transformation of a normal subset of CD20+ T cells rather than aberrant antigen expression by neoplastic cells. The nature of the CD20 antigen on T cells and the function of the normal population remain to be determined.
CD20是一种35千道尔顿的蛋白质，在B细胞发育早期表达，在B细胞终末分化为浆细胞的过程中消失。它被认为是B细胞特异性的。然而，通过单克隆抗体L26检测到的CD20抗原在一些T细胞淋巴瘤病例中也有报道。本报告描述了一例同时表达T细胞系抗原和CD20的恶性淋巴瘤病例，以及健康供体外周血中CD20+ T细胞群体的特征。肿瘤细胞为多形性中等大小细胞，表达一系列T细胞特异性抗原，包括CD2、CD3、CD4、CD5、CD6、CD7和βF1。此外，肿瘤细胞在冰冻切片（B1）和石蜡切片（L-26）上均表达CD20。对包括CD19和CD22在内的其他全B细胞抗原以及免疫球蛋白轻链和重链的染色均为阴性。为了确定这种T细胞系抗原和CD20的异常共表达是代表异常抗原表达还是异常正常T细胞亚群的肿瘤转化，作者通过流式细胞术使用三色免疫荧光分析检查了健康供体外周血淋巴细胞标本中CD20+ T细胞群体的证据。在外周血中观察到两个不同的CD20+细胞群体。一个群体表达明亮的CD20（占外周血淋巴细胞的6.6%至23.7%，平均14.47%）和其他B细胞相关抗原，而另一个群体表达暗淡的CD20（占外周血淋巴细胞的0.94%至11.90%，平均3.50%）并共表达CD3。大约三分之二（52.8%至82.3%，平均64.1%）的暗淡CD20细胞为CD8+，三分之一（19.2%至74.1%，平均37.5%）为CD4+。这些细胞还表达CD5和T细胞受体的α-β链，且缺乏CD19和CD22。这些结果表明，一些正常外周血T细胞表达CD20。T细胞淋巴瘤中CD20的表达可能代表正常CD20+ T细胞亚群的肿瘤转化，而非肿瘤细胞的异常抗原表达。T细胞上CD20抗原的性质以及正常群体的功能仍有待确定。
