CD4⁺CD62L⁻CD45RO⁺ FL TILs, but not the corresponding autologous PBMC T cells, have reduced cytokine signaling capacity. IL-4–induced phosphorylation of p-STAT6 was analyzed in malignant LN and in autologous PBMC samples from patients with FL by combining CD3-, CD5-, CD4-, CD8-, CD62L-, and CD45RO-specific Abs with p-STAT6 Ab in the phospho-flow cytometric assay. (A) Gating strategy of live cells to identify CD3⁺CD4⁺ T cells and then subsequent gating on the basis of expression of CD62L and CD45RO to identify CD62L⁺CD45RO⁻, CD62L⁺CD45RO⁺, CD62L⁻CD45RO⁺ cells, and the corresponding histograms of IL-4–induced p-STAT6 in the various CD4⁺ T-cell subsets. (A) Representative FACS data from 1 patient with FL are shown and (B) mean FC of IL-4–induced p-STAT6⁺ cells in CD4⁺ T subsets from FL LN and autologous PBMCs. Mean ± SEM, n = 5. (C) Mean FC of IL-4–induced p-STAT6 relative to unstimulated cells in CD4⁺ T subsets from tonsil and autologous blood samples from healthy tonsil donors. Mean ± SEM, n = 3. Significance between groups was determined by unpaired 2-tailed Student t test.