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Published on: August 5, 2011
Human Lyb-2 homolog CD72 is a marker for progenitor B-cell leukemias
R Schwarting1, R Castello, G Moldenhauer
1Department of Pathology, Thomas Jefferson University, Philadelphia, PA 19107.
Insights
The CD72 antigen, identified by the S-HCL 2 monoclonal antibody, is expressed on most B lymphocytes and some tissue macrophages. CD72 is a potential diagnostic marker for B-cell leukemias and lymphomas.
Area of Science:
- Immunology
- Hematology
- Oncology
Background:
- The CD72 antigen, also known as human Lyb-2, is a recently defined cluster.
- The S-HCL 2 monoclonal antibody (mAb) is the prototype antibody for CD72.
- Understanding CD72 expression is crucial for differentiating B-cell malignancies.
Purpose of the Study:
- To characterize the expression of the CD72 antigen in normal and malignant tissues.
- To evaluate the utility of the S-HCL 2 mAb as a diagnostic marker for B-cell neoplasms.
Main Methods:
- Immunoprecipitation under reducing and nonreducing conditions to analyze CD72 protein structure.
- Immunohistochemical staining of normal and malignant tissues to assess CD72 distribution.
- Flow cytometry analysis of leukemic cells to determine CD72 expression across B-cell differentiation stages.
Main Results:
- S-HCL 2 mAb precipitates a 80-86 kDa glycoprotein under nonreducing conditions, and a dimer of 43/39 kDa under reducing conditions.
- CD72 is expressed on B lymphocytes (except plasma cells) in peripheral blood and bone marrow.
- Distinct CD72 positivity was observed in splenic red pulp macrophages and Kupffer cells.
- All tested B-cell lymphomas (54/54) and B-cell leukemias (52/52) showed CD72 expression, including early B-cell precursors.
- No T-cell lymphomas exhibited CD72 positivity.
Conclusions:
- CD72 expression differs significantly from other human B-cell antigens.
- CD72 is a reliable marker for B-cell lineage identification in both normal and malignant hematopoiesis.
- CD72, detected by S-HCL 2 mAb, shows promise as a valuable diagnostic marker for progenitor B-cell leukemias and lymphomas.
Abstract:
S-HCL 2 is the prototype antibody of the recently defined CD72 cluster (human Lyb-2). Under nonreducing conditions, S-HCL 2 monoclonal antibody (mAb) precipitates a glycoprotein of 80-86 kDa. Under reducing conditions, a dimer of 43 and 39 kDa, with core proteins of 40 and 36 kDa, is precipitated. CD72 expression in normal and malignant tissues is different from expression of all other previously described human B-cell antigens. In peripheral blood and bone marrow, the antigen appears to be present on all B lymphocytes, with the exception of plasma cells. In tissue, immunohistochemical staining revealed positivity for all known B-cell compartments; however, pulpa macrophages of the spleen and von Kupffer cells exhibited distinct positivity for CD72 also. Among 83 malignant non-Hodgkin's lymphomas examined by immunohistochemistry (alkaline phosphatase anti-alkaline phosphatase technique), all 54 B-cell lymphomas, including precursor B-cell lymphomas, Burkitt's lymphomas, germinal center lymphomas, chronic lymphocytic leukemias, and hairy cell leukemias, were CD72 positive, but no T-cell lymphomas were. Flow cytometry study of more than 80 mainly acute leukemias (52 B-cell leukemias) showed reactivity with S-HCL 2 mAb over the full range of B-cell differentiation. In particular, very early B cells in cytoplasmic Ig (cIg)-negative, CD19-positive pre-pre-B-cell leukemias and hybrid leukemias (mixed myeloid and B-cell type) were consistently positive for CD72 on the cell surface. Therefore, CD72 may become an important marker for progenitor B-cell leukemias.
