title: B cell activation is regulated by the stiffness properties of the substrate presenting the antigens.
abstract: B lymphocytes are activated upon Ag sensing by BCRs. The substrate presenting the Ag can show different degrees of stiffness. It is not clear whether B cells can respond to changes in substrate stiffness. In this study we use high-resolution, high-speed live cell imaging techniques to capture the molecular events in B cell activation after the recognition of Ags tethered to polyacrylamide gel substrates with variable degrees of stiffness as quantified by Young's modulus (2.6-22.1 kPa). We show that the initiation of B cell activation is extremely sensitive to substrate stiffness. B cells exhibit much stronger activation responses when encountering Ags tethered to substrates with a high degree of stiffness as measured by the accumulation of BCR, phospho-spleen tyrosine kinase, and phosphotyrosine molecules into the B cell immunological synapse. Ags tethered to stiff substrates induce the formation of more prominent BCR and phospho-spleen tyrosine kinase microclusters with significantly enhanced colocalization as compared with Ags tethered to soft substrates. Moreover, the expression of the B cell activation marker CD69 is enhanced in B cells encountering Ags on stiffer substrates. Through time-lapse live cell imaging, we find that the different responses of B cells to substrate stiffness are only demonstrated 5 min after BCR and Ag recognition. Using a series of cytoskeleton inhibitors, we determine that the mechanosensing ability of B cells is dependent on microtubules, and only mildly linked to the actin cytoskeleton. These results suggest the importance of the mechanical properties mediated by substrate stiffness in B cell activation.
authors.affiliation: MOE Key Laboratory of Protein Science, [corrected] School of Life Sciences, Tsinghua University, Beijing 100084, China.
authors.forename: Zhengpeng
authors.initials: Z
authors.lastname: Wan
authors.forename: Shaosen
authors.initials: S
authors.lastname: Zhang
authors.forename: Yilin
authors.initials: Y
authors.lastname: Fan
authors.forename: Kai
authors.initials: K
authors.lastname: Liu
authors.forename: Feng
authors.initials: F
authors.lastname: Du
authors.forename: Angel M
authors.initials: AM
authors.lastname: Davey
authors.forename: Huiyuan
authors.initials: H
authors.lastname: Zhang
authors.forename: Weidong
authors.initials: W
authors.lastname: Han
authors.forename: Chunyang
authors.initials: C
authors.lastname: Xiong
authors.forename: Wanli
authors.initials: W
authors.lastname: Liu
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000276:immunology*; D000941:Antigens / Q000276:immunology*; D015703:Antigens, CD / Q000276:immunology / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology / Q000378:metabolism; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D003599:Cytoskeleton / Q000276:immunology / Q000378:metabolism; D037181:Lectins, C-Type / Q000276:immunology / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D011505:Protein-Tyrosine Kinases / Q000276:immunology / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000276:immunology / Q000378:metabolism; D000099192:CD69 Antigens
chemical_list: D000941:Antigens; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D037181:Lectins, C-Type; D011505:Protein-Tyrosine Kinases; D011947:Receptors, Antigen, B-Cell; D000099192:CD69 Antigens