Mouse T cell priming is enhanced by maturation-dependent stiffening of the dendritic cell cortex

Abstract

T cell activation by dendritic cells (DCs) involves forces exerted by the T cell actin cytoskeleton, which are opposed by the cortical cytoskeleton of the interacting APC. During an immune response, DCs undergo a maturation process that optimizes their ability to efficiently prime naïve T cells. Using atomic force microscopy, we find that during maturation, DC cortical stiffness increases via a process that involves actin polymerization. Using stimulatory hydrogels and DCs expressing mutant cytoskeletal proteins, we find that increasing stiffness lowers the agonist dose needed for T cell activation. CD4+ T cells exhibit much more profound stiffness-dependency than CD8+ T cells. Finally, stiffness responses are most robust when T cells are stimulated with pMHC rather than anti-CD3ε, consistent with a mechanosensing mechanism involving receptor deformation. Taken together, our data reveal that maturation-associated cytoskeletal changes alter the biophysical properties of DCs, providing mechanical cues that costimulate T cell activation.

Mechanosensitivity of amoeboid cells crawling in 3D

“…In this reductionist approach, no pre-formed space is available and the highly flattened cells need to actively lift and deform the agarose to create sufficient space between coverslip and agarose (Figure 1A) (Laevsky and Knecht, 2003). To precisely control the mechanical load that the cells have to counter, we adjusted the stiffnesses of the agarose around the range of cellular stiffness as measured by atomic force microscopy (AFM) (Blumenthal et al, 2020;Guimarães et al, 2020) (Figures 1A, S1A). With increasing load, the mean migratory speed declined (Figures 1B,C, S1B) and the cells shifted from continuous locomotion to a stop and go pattern where cells collapsed and stalled after short stretches of movement (Figure 1D, Movie S1).…”

Soft Polydimethylsiloxane-Supported Lipid Bilayers for Studying T Cell Interactions

“…Interestingly, they also found that on the softer gels, the phosphorylated kinases did not form microclusters, suggesting that microcluster formation requires a degree of substrate resistance, more so than receptor triggering per se. Blumenthal et al observed much greater effects of hydrogel stiffness on CD4 þ than on CD8 þ T cells, also suggesting that whatever mechanism conveys substrate-stiffness effects to the cell lies downstream of the TCR (35). It could be argued that 4-to 10-kPa surfaces are rigid enough to create the tension needed to mechanically trigger the TCR, but even lower levels of rigidity appear to allow TCR triggering.…”

Nanowire Based Guidance of the Morphology and Cytotoxic Activity of Natural Killer Cells

“…Furthermore, it has been recently reported during the maturation of dendritic cells, their cortical stiffness changes, and that this change alters the activation ability of T cells by dendritic cells. [ 26 ] Finally, it was shown that within the 3D nanomorphology shown at the interface between a cytotoxic lymphocyte and antigen‐presenting cells, the ligand‐receptor complexes are concentrated at the tips of nanoscale protrusions. [ 10 ] Understanding the role of all the above mentioned physical parameters of the interface between the lymphocyte and antigen‐presenting cells—nanoscale topography, stiffness, and position of signaling receptors—can be facilitated by a nanoengineered platform that independently controls these parameters.…”

“…Such cumulative effect is produced in vivo by dendritic cells, whose distinct morphology, mechanical stiffness, and expression of antigens jointly determine the immune function of cytotoxic lymphocytes. [ 26 ] Yet, a biomimetic platform that can systematically reproduce these stimuli ex vivo has not been reported up until now.…”