Fig. 1

B cells show antigen-specific pulsatile traction forces on PAA gels. a Cartoon of traction force microscopy showing B-cell plated on antigen-coated polyacrylamide (PAA) gel containing fiducial markers. b Scanning electron microscopy of fixed B lymphocytes on HEL-coated glass and PAA gels, scale bar is 2 µm. c Time-lapse color maps of stress for HEL and control BSA condition; contractile stress can reach 70 Pa. d Comparison of average strain energy profile for HEL and BSA conditions, error bars represent mean ± SEM (n = 65 for HEL and n = 35 for BSA, five independent experiments, five mice), acquisitions were started before the arrivals of the cells to capture the initial time of contact and all cells were aligned at time zero. e Summary statistics of plateau of strain energy for HEL and BSA, error bar represents median ± IQR (n = 65 for HEL and n = 35 for BSA, five independent experiments, five mice), Mann–Whitney test was performed for statistical analysis. f Concentration-dependent increase in strain energy, error bars representing median ± IQR (n = 12, 13, 15, 16, 3 independent experiments, three mice), Mann–Whitney test was performed for statistical analysis. g Example of the strain energy curve for a single cell, plateau exhibit isolated peaks (see single stress maps). h Extraction of the typical pulsation frequency from the contractile energy: from the time series of a coordinated energy signal (smoothed in red), the signal is de-trended and the power spectrum density derived from it shows a maximum, hence a typical time scale for the pulsation. i Displacement flux showing the direction of displacement over time in HEL and BSA condition (mean ± SEM, n = 65 for HEL and n = 35 for BSA, five independent experiments, five mice). Source data are provided as a Source Data file