Figure 5.

Close contact between Ki67^pos cells and follicular helper T cells in follicular lymphoma: evidence for immune synapse formation. (A1) A Ki67^pos cell (red) is seen to be in contact with 4 PD-1^pos (white) ICOS^pos (green) cells simultaneously. The PD-1^posICOS^pos cells are closely associated with the Ki67^pos cell. (A2) Binary layer image of A1, the binary layers of Ki67 (red) and PD-1/ICOS intersection (magenta) are shown highlighting the close spatial association. Scale bars represent 10 μm. (B1) The follicular helper T cells (T_FH) form projections encompassing the Ki67^pos cells. Scale bar represents 10 μm. The perimeter of the T_FH has been highlighted by the red dotted line and the intensity of CD4, PD-1 and ICOS have been measured around this line. CD4, PD1 and ICOS are more concentrated at the pole in contact with the Ki67^pos cell as seen in the representative graph of intensity of expression around the dotted line, the area of cell contact is highlighted in the shaded area (B2). (B3) CD4, PD1, and ICOS all have significantly higher intensity of expression at the sites of cell contact than at the opposite pole, paired t-tests, n=61 cell con-tacts, from highly magnified images in nine follicular lymphoma specimens stained with CD4/PD-1/Ki67, or PD-1/ICOS/Ki67. AUC: area under the curve.