B cell activation is regulated by the stiffness properties of the substrate presenting the antigens

• Published in: The Journal of immunology (1950) Vol. 190; no. 9; pp. 4661 - 4675
• Main Authors: Wan, Zhengpeng, Zhang, Shaosen, Fan, Yilin, Liu, Kai, Du, Feng, Davey, Angel M, Zhang, Huiyuan, Han, Weidong, Xiong, Chunyang, Liu, Wanli
• Format: Journal Article
• Language: English
• Published: United States 01.05.2013
• Subjects: Animals; Antigen Presentation - immunology; Antigens - immunology; Antigens, CD - immunology; Antigens, CD - metabolism; Antigens, Differentiation, T-Lymphocyte - immunology; Antigens, Differentiation, T-Lymphocyte - metabolism; B-Lymphocytes - immunology; B-Lymphocytes - metabolism; Cytoskeleton - immunology; Cytoskeleton - metabolism; Lectins, C-Type - immunology; Lectins, C-Type - metabolism; Lymphocyte Activation - immunology; Mice; Mice, Inbred BALB C; Protein-Tyrosine Kinases - immunology; Protein-Tyrosine Kinases - metabolism; Receptors, Antigen, B-Cell - immunology; Receptors, Antigen, B-Cell - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.1202976

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.