CD20 (Pan-B Cell Antigen) Expression on Bone Marrow-Derived T Cells

Abstract

Antibodies directed against CD20 (L26, Leu 16, and Bl) are frequently used to determine the presence of B lymphocytes. However, recent publications describe the unexpected presence of CD20-positive T cells in the peripheral blood of normal subjects and occasional T-cell neoplasms that express CD20. To determine the presence of CD20-positive T cells in bone marrow, flow cytometric analysis was performed on 34 aspirate specimens (14 normal, 5 acute lymphoblastic lymphoma |ALL|, 5 acute myelogenous leukemia |AML|, 4 HIV positive, 2 myelodysplastic/myeloproliferative, 2 chronic myelogenous leukemia |CML|, 1 chronic lymphocytic lymphoma |CLL], 1 multiple myeloma). A small population of cells coexpressing CD3 (Leu 4) and CD20 dim (Leu 16) was identified in 94% of the specimens, representing 0% to 11%Phenotyping of human lymphoid proliferations is of value in determining cell lineage. Immunophenotyping uses monoclonal antibodies directed against B-or T-cell specific antigens. B lymphocytes are identified by the presence of the antigens CD 19, CD20, CD21, and CD22. CD20 is a 33-kDa membrane phosphoprotein' with three hydrophobic regions that traverse the cell membrane, creating a structure similar to an ion channel. 2This protein is expressed on the majority of B cells, appearing early in B-cell development (following CD 19 and CD 10, but preceding CD21, cell surface expression of CD22, and surface immunoglobulin). "5 CD20 is retained on mature B cells until plasma cell development. 34 The CD20 antigen can be identified by immunohistochemistry or flow cytometry using several commercially available monoclonal antibodies: Leu 16, Bl, and L26 (Leu 16

Reconstitution of peripheral blood B cells after depletion with rituximab in patients with rheumatoid arthritis

“…These cells disappeared from the circulation for a mean of 5 months following treatment with rituximab. Previous reports had described the presence of T cells expressing low levels of CD20 in the peripheral blood (25)(26)(27). We did not observe significant changes in the total number or frequency of the other peripheral blood T cell populations studied, except for a transitory decrease in the frequency of CD4ϩ,CD25ϩϩ T cells (regulatory T cells) at 1 month.…”

High Levels of CD2 Expression Identify HIV-1 Latently Infected Resting Memory CD4+T Cells in Virally Suppressed Subjects

“…These studies suggest the possibility of targeting CD2 for the depletion of latently infected CD4 ϩ T cells in HIV-1 infection. Although CD2 is also expressed on uninfected T and NK cells, the FDA has approved targeting of receptors such as CD20 for cell depletion in autoimmune diseases and cancer, despite the fact that CD20 is also expressed on normal B and T cells (78,79).…”

Circulating CD20 is detectable in the plasma of patients with chronic lymphocytic leukemia and is of prognostic significance

“…CD20, also called B1 (Bp35), is a phosphoprotein detected on the surface of B lymphocytes [1][2][3] and believed to play a major role in the regulation, activation, proliferation, and differentiation of these cells. [4][5][6] The gene for CD20 has been mapped to human chromosome 11 at position q12-q13, centromeric to the Bcl-1 locus, which is involved in the translocation t(11;14)(q13;q32).…”