(E) Representative confocal micrographs of p-tyrosine (p-Tyr) polarization at B-T cell contacts after 1-2h of co-culture. Cell conjugates were stained with anti-pTyr antibody. Scale bar, 5µm. The top panels display only the p-Tyr signal in grey, the bottom panel depicts p-Tyr (red), BHEL cells (blue) and CD4OT-II cells (green). (F) Quantification of p-Tyr accumulation at the B-T interface as shown in E. Shown are mean values with SD from three independent experiments with at least 50 conjugates analyzed per experiment. 