title: Polymeric C3dg primes human B lymphocytes for proliferation induced by anti-IgM.
abstract: Polymeric C3dg (pC3dg), having an average m.w. of approximately 400,000 and saturating complement receptor type 2 (CR2) on B lymphoblastoid cells at 1 micrograms/ml, was preincubated with tonsillar B cells for 24 h, after which anti-IgM was added and proliferation assessed by thymidine incorporation. Preculture of B cells with 0.01 to 1.0 micrograms/ml of polymerized C3dg (pC3dg) caused a dose-dependent enhancement of proliferation and accelerated entry into S phase after addition of anti-IgM. The continued presence of pC3dg during stimulation by anti-IgM was not required. pC3dg alone did not induce proliferation and preculture of B cells with C3dg monomer had no effect on the subsequent response to anti-IgM. The priming effect of pC3dg required at least 6 h and was greatest after 24 h of preculture. Preincubation with pC3dg did not lower the concentration of anti-IgM necessary for induction of proliferation, but did enhance proliferation at all concentrations above this threshold. Augmented proliferation occurred only in B cells of higher density in Percoll gradients, and neither T cells nor monocytes were required. Thus, independent interaction of CR2 with its natural ligand primes the B cell for subsequent stimulation through the Ag receptor, an effect that might synergize with the previously described CR2 function of lowering the threshold for B cell activation when crosslinked to membrane IgM.
authors.affiliation: Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205.
authors.forename: R H
authors.initials: RH
authors.lastname: Carter
authors.forename: D T
authors.initials: DT
authors.lastname: Fearon
mesh_terms: D000888:Antibodies, Anti-Idiotypic / Q000502:physiology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology*; D003176:Complement C3 / Q000378:metabolism; D003179:Complement C3b / Q000378:metabolism / Q000502:physiology*; D004306:Dose-Response Relationship, Immunologic; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology* / Q000502:physiology; D008213:Lymphocyte Activation; D046911:Macromolecular Substances; D014066:Palatine Tonsil; D010446:Peptide Fragments / Q000378:metabolism / Q000502:physiology*; D011951:Receptors, Complement / Q000378:metabolism; D017464:Receptors, Complement 3d
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000944:Antigens, Differentiation, B-Lymphocyte; D003176:Complement C3; D007075:Immunoglobulin M; D046911:Macromolecular Substances; D010446:Peptide Fragments; D011951:Receptors, Complement; D017464:Receptors, Complement 3d; C044203:anti-IgM; C045477:complement C3d,g; D003179:Complement C3b