title: Distinct signal thresholds for the unique antigen receptor-linked gene expression programs in mature and immature B cells.
abstract: Although it is well established that immature B lymphocytes are exquisitely sensitive to tolerance induction compared with their mature counterparts, the molecular basis for this difference is unknown. We demonstrate that signaling by B cell antigen receptors leads to distinct and mutually exclusive biologic responses in mature and immature B cells: upregulation of CD86, CD69, and MHC class II in mature cells and receptor editing in immature cells. These responses can be induced simply by elevation of intracellular free calcium levels, as occurs after receptor aggregation. Importantly, induction of immature B cell responses requires much smaller increases in intracellular free calcium than does induction of mature B cell responses. These differences in biologic response and sensitivity to intracellular free calcium likely contributes to selective elimination at the immature stage of even those B cells that express low affinity for self-antigens.
authors.affiliation: Division of Basic Sciences, Department of Pediatrics, National Jewish Medical and Research Center, University of Colorado Health Sciences Center, Denver 80206, USA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Benschop
authors.forename: D
authors.initials: D
authors.lastname: Melamed
authors.forename: D
authors.initials: D
authors.lastname: Nemazee
authors.forename: J C
authors.initials: JC
authors.lastname: Cambier
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000235:genetics / Q000276:immunology; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D051940:B7-2 Antigen; D002454:Cell Differentiation / Q000276:immunology; D005786:Gene Expression Regulation / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology; D037181:Lectins, C-Type; D008562:Membrane Glycoproteins / Q000235:genetics / Q000276:immunology; D051379:Mice; D008822:Mice, Transgenic; D017393:RNA Editing / Q000276:immunology; D011947:Receptors, Antigen, B-Cell / Q000235:genetics* / Q000276:immunology; D015854:Up-Regulation; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D051940:B7-2 Antigen; D000949:Histocompatibility Antigens Class II; D037181:Lectins, C-Type; D008562:Membrane Glycoproteins; D011947:Receptors, Antigen, B-Cell; D000099192:CD69 Antigens; C497965:Cd86 protein, mouse