title: Ligation of CD40 influences the function of human Ig-secreting B cell hybridomas both positively and negatively.
abstract: The effect of ligation of CD40 on the proliferation and Ig secretion of a battery of human Ig-secreting hybridomas was examined to determine the regulatory activity of this surface molecule on B cells after initial activation. B cell hybridomas were generated by fusing activated peripheral blood B cells with SPAZ-4, a non-Ig-secreting fusion partner, and were cloned before analysis. All hybridomas expressed CD40 comparably. These hybridomas were stimulated with either recombinant baculovirus-expressed membrane-bound CD40L or a soluble murine CD40L/CD8 construct in the presence or the absence of various cytokines. Concentrations of CD40L that saturated 40 to 100% of CD40 induced initial homotypic aggregation followed by Fas (CD95)-independent apoptosis, with resultant decreases in growth and Ig secretion. Concentrations of CD40L that saturated 15 to 25% of CD40 also stimulated aggregation of all hybridomas. However, proliferation and Ig secretion of 9 of 13 IgM-secreting hybridomas, but none of 14 IgG- or IgA-secreting hybridomas, were enhanced by these concentrations of CD40L. These responses were independent of interactions mediated by the adhesion pair CD1la/CD18-CD54. These results indicate that the impact of CD40 ligation on human Ig-secreting hybridomas varies with the extent of CD40 engagement and depending on whether the hybridoma derived from an activated B cell that had previously undergone switch recombination.
authors.affiliation: Harold C. Simmons Arthritis Research Center, University of Texas Southwestern Medical Center, Dallas 75235, USA.
authors.forename: M C
authors.initials: MC
authors.lastname: Bergman
authors.forename: J F
authors.initials: JF
authors.lastname: Attrep
authors.forename: A C
authors.initials: AC
authors.lastname: Grammer
authors.forename: P E
authors.initials: PE
authors.lastname: Lipsky
mesh_terms: D000328:Adult; D000818:Animals; D017209:Apoptosis / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D001483:Base Sequence; D015415:Biomarkers / Q000032:analysis; D019013:CD40 Antigens / Q000096:biosynthesis / Q000378:metabolism*; D023201:CD40 Ligand; D002449:Cell Aggregation / Q000276:immunology; D006801:Humans; D006825:Hybridomas / Q000276:immunology / Q000378:metabolism*; D007136:Immunoglobulins / Q000096:biosynthesis; D008024:Ligands; D008213:Lymphocyte Activation; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000276:immunology
chemical_list: D015415:Biomarkers; D019013:CD40 Antigens; D007136:Immunoglobulins; D008024:Ligands; D008562:Membrane Glycoproteins; D023201:CD40 Ligand