Natural Killer cell immune synapse formation and cytotoxicity is controlled by mechanical tension of the target

• Published in: The Journal of immunology (1950) 2020-05, Vol.204 (1_Supplement), p.74-74.3
• Main Authors: Simmonds, P, Friedman, Daniel, Hale, Alexander, Hodson, Nigel W, White, Michael RH, Davis, Daniel M
• Format: Article
• Language: English
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.204.Supp.74.3

Natural Killer (NK) cells can kill infected or transformed cells directly via the formation of a lytic synapse at the cell-cell interface. Diseased cells often present with altered mechanical properties, and cell stiffness is a feature of tumour cell migratory potential. However, little is known about how target cell stiffness impacts the assembly of the NK cell synapse or the subsequent functional response. To study this, we set out to create surrogate targets with specific ligands presented on cell-sized beads of different stiffness. Sodium alginate cell-sized microbeads were synthesised where chemical composition was altered to produce beads of low (9kPa), medium (34kPa), or high (254kPa) stiffness. These were coated with antibodies against the NK cell activating receptor NKp30 and the integrin LFA-1 to model the 3D interaction between NK cells and target cells. Imaging revealed that later steps in NK-cell activation differed significantly, including the degree of cytoskeletal arrangement, F-actin accumulation, microtubule organising centre polarisation and perforin accumulation. Stiffer beads induced polarisation of the MTOC in 59% of conjugates analysed compared to only 7% with low stiffness targets. Functionally, NK cell degranulation was higher when forming conjugates with stiffer targets. The metabolic profiles were similar between NK cells stimulated overnight by antibody-coated beads, regardless of their stiffness. Altogether, these data imply that stiffer targets are more potent in triggering the initial activating signals in NK cells. Thus, immune synapse mechanosensitivity represents a novel form of NK cell regulation.