(I) Representative confocal images of the subcellular distribution of IL-4 in CD4OT-II cells expressing the indicated proteins engaged in an IS with BHEL cells. B cells and T cells were placed on PLL-coated cover glasses for 60-90min, fixed and stained for intracellular IL-4. Filled and empty arrowheads indicate presence or absence of IL-4 accumulation at the IS, respectively. Scale bars, 5µm. (J) Quantification of IL-4 accumulation at the IS as depicted in I. Shown are mean values with SD from 3 independent experiments relative to control cells set to 100%. 