A significant fraction of a-CASP3⁺ cells is detected in contact with CD8⁺GrzB⁺ cells. Tissue sections from FL lymph nodes were stained for CD8 (green), a-CASP3 (blue) and GrzB (red). (A) Representative staining showing contact formation between CD8⁺GrzB⁺ cells and a-CASP3⁺ cells in a FL lymph node (bar = 5 μm). (B) Scoring of the total number of a-CASP3⁺ cells interacting with CD8⁺ or GrzB⁺ cells in 7 FL lymph nodes. The analysis was performed by scoring the fields using 3-D reconstructed images to unambiguously define cellular contacts (see “Confocal Image Quantification”). Statistical significance of difference between groups was evaluated by a paired Student t test using STATA Version 11; P = .0006.