title: Conditional immortalization of human B cells by CD40 ligation.
abstract: It is generally assumed that human differentiated cells have a limited life-span and proliferation capacity in vivo, and that genetic modifications are a prerequisite for their immortalization in vitro. Here we readdress this issue, studying the long-term proliferation potential of human B cells. It was shown earlier that human B cells from peripheral blood of healthy donors can be efficiently induced to proliferate for up to ten weeks in vitro by stimulating their receptor CD40 in the presence of interleukin-4. When we applied the same stimuli under conditions of modified cell number and culture size, we were surprised to find that our treatment induced B cells to proliferate throughout an observation period of presently up to 1650 days, representing more than 370 population doublings, which suggested that these B cells were immortalized in vitro. Long-term CD40-stimulated B cell cultures could be established from most healthy adult human donors. These B cells had a constant phenotype, were free from Epstein-Barr virus, and remained dependent on CD40 ligation. They had constitutive telomerase activity and stabilized telomere length. Moreover, they were susceptible to activation by Toll-like receptor 9 ligands, and could be used to expand antigen-specific cytotoxic T cells in vitro. Our results indicate that human somatic cells can evade senescence and be conditionally immortalized by external stimulation only, without a requirement for genetic manipulation or oncoviral infection. Conditionally immortalized human B cells are a new tool for immunotherapy and studies of B cell oncogenesis, activation, and function.
authors.affiliation: Clinical Cooperative Group Molecular Oncology, GSF - National Research Center, Ludwig-Maximilians-Universität, Munich, Germany.
authors.forename: Martina
authors.initials: M
authors.lastname: Wiesner
authors.forename: Caroline
authors.initials: C
authors.lastname: Zentz
authors.forename: Christine
authors.initials: C
authors.lastname: Mayr
authors.forename: Rainer
authors.initials: R
authors.lastname: Wimmer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Hammerschmidt
authors.forename: Reinhard
authors.initials: R
authors.lastname: Zeidler
authors.forename: Andreas
authors.initials: A
authors.lastname: Moosmann
mesh_terms: D001402:B-Lymphocytes / Q000166:cytology* / Q000201:enzymology / Q000648:ultrastructure; D019013:CD40 Antigens / Q000378:metabolism*; D002461:Cell Line, Transformed; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D008213:Lymphocyte Activation; D019098:Telomerase / Q000378:metabolism; D016615:Telomere
chemical_list: D019013:CD40 Antigens; D019098:Telomerase