title: Membrane fluidity and lipid hapten structure of liposomes affect calcium signals in antigen-specific B cells.
abstract: Antigen-specific B-cell clones directed against a 2,4,6-trinitrophenyl (TNP) hapten have been established [Hamano et al. (1990) J. Immunol. 144, 811-815]. We measured here the cytosolic free calcium ion concentration ([CA2+]i) in these B-cell clones after antigen stimulation. Trinitrophenylated liposomes with different length spacers between TNP and phosphatidylethanolamine (TNP-Cn-PE) increased cytosolic free calcium concentration in TNP-specific B cells (clone TP67.21). The magnitude of calcium signals depended on the length of the spacer. TNP-C6-PE in dipalmitoylphosphatidylcholine (DPPC) liposomes triggered larger calcium signals in B cells than TNP-Cn-PE with n = 0, 4, 8, or 12. The magnitude of the calcium signals was strongly dependent on the fluidity of the liposome membranes. TNP-C6-PE in the solid DPPC liposomes triggered the calcium signals in B cells 50-100 times as efficiently as TNP-C6-PE in the fluid dimyristoylphosphatidylcholine liposomes. The difference between the solid liposomes and the fluid liposomes was more pronounced in triggering calcium signals in B cells than in antibody binding to these liposomes.
authors.affiliation: Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Ohyama
authors.forename: T
authors.initials: T
authors.lastname: Hamano
authors.forename: N
authors.initials: N
authors.lastname: Hamakawa
authors.forename: K
authors.initials: K
authors.lastname: Inagaki
authors.forename: M
authors.initials: M
authors.lastname: Nakanishi
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000737:chemistry / Q000276:immunology*; D002118:Calcium / Q000276:immunology / Q000502:physiology*; D000939:Epitopes / Q000737:chemistry; D006241:Haptens / Q000737:chemistry* / Q000276:immunology; D006825:Hybridomas; D008055:Lipids / Q000737:chemistry* / Q000276:immunology; D008081:Liposomes / Q000737:chemistry* / Q000276:immunology; D008560:Membrane Fluidity; D015398:Signal Transduction; D014301:Trinitrobenzenes / Q000276:immunology
chemical_list: D000939:Epitopes; D006241:Haptens; D008055:Lipids; D008081:Liposomes; D014301:Trinitrobenzenes; D002118:Calcium