Background and methods: CD5 is a monomeric glycoprotein expressed on normal and malignant T cells and on chronic lymphocytic leukemia cells. Murine anti-CD5 monoclonal antibodies (MAbs) were obtained using T cell lines, thymocytes, and blast cells from acute T lymphoblastic leukemia as immunogen. In the present report we describe an anti-CD5 MAb obtained from hybridization of mouse spleen lymphocytes immunized with blast cells from a patient with plasmocytoma who underwent leukemic transformation.
Results and conclusions: We demonstrate that this MAb arises from the CD5 determinant of lymphocytes disseminated among the leukemic cells. We present initial characterization of this MAb, which may represent a new CD5 epitope. Potentially, due to its efficient internalization through the cell membrane, this MAb might be used to deliver toxins to immunocompetent T lymphocytes for prevention of acute graft-versus-host disease (aGVHD) after bone marrow transplantation.