Antibody affinity may influence antigenic modulation of the common acute lymphoblastic leukemia antigen in vitro

T. W. Lebien, D. R. Boue, J. G. Bradley, J. H. Kersey

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79 Scopus citations

Abstract

We have produced a new monoclonal antibody designated BA-3. An extensive side-by-side serologic comparison of BA-3 with the anti-common acute lymphoblastic leukemia antigen (CALLA) monoclonal antibody J-5 was undertaken. Cells examined included established leukemic cell lines, malignant cells from patients with newly diagnosed leukemia/lymphoma, and normal hematopoietic tissues. In all experiments the cellular distribution of the antigens recognized by BA-3 and J-5 were identical when analyzed by immunofluorescent microscopy and the FACS. Iodination of NALM-6 cells, followed by radioimmunoprecipitation and SDS-PAGE, indicated that BA-3 (like J-5) precipitated a glycoprotein of approximately 100,000 daltons. Competitive binding studies using 125I-labeled BA-3 indicated that B-3 and J-5 were binding to closely associated (if not identical) epitopes on CALLA. Calculation of the equilibrium constant (K value) for BA-3 and J-5, and the approximate number of CALLA molecules per cell, was graphically determined using Scatchard plots. BA-3 and J-5 were shown to have K values of approximately 2.7 X 107 M-1 and 7.2 x 107 M-1 respectively, with NALM-6 cells expressing 1 x 105 to 2 x 105 CALLA molecules per cell. Additional studies with BA-3 failed to demonstrate significant antigenic modulation of CALLA in vitro using fresh leukemic cells and leukemic cell lines. Thus, we suggest that antibody affinity may be a significant factor influencing antigenic modulation of CALLA in vitro.

Original languageEnglish (US)
Pages (from-to)2287-2292
Number of pages6
JournalJournal of Immunology
Volume129
Issue number5
StatePublished - 1982

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