Step 1, gate cells in best focus (R1). Step 2, gate conjugates (R2). Single cells (intermediate area value and high aspect ratio) are excluded. Step 3, gate CD3 and CD19 double positive (R3, FITC+PE+). Step 4, gate conjugates with only one target cell (R4). Step 5, gate conjugates with only one effector cell (R5). This subpopulation consists of doublets with only one effector and one target cell. Step 6, gate immunological synapse (R6). 'Valley’ mask is employed to quantify actin intensity in the region of contact (Bright detail intensity). Co-localization wizard is used to measuring overlap (Bright detail similarity). For technical details, please see the user’s manual of IDEAS.