Tumor-infiltrating T cells in FL biopsies have suppressed cytokine signaling. Tumor specimens from patients with DLBCL, MCL, FL, or CLL or PBMCs from healthy donors were stimulated with cytokines for 15 minutes. Signaling was then stopped by fixation, followed by permeabilization and detection of cytokine-induced phosphorylation of STATs by phospho-flow cytometry. (A) Representative FACS plots of TILs or normal PBMC T cells were identified on the basis of their coexpression of CD3 and CD5, lack of CD20 expression, and histograms of IL-4–induced p-STAT6 and IL-21–induced p-STAT3 in TILs from a FL tumor sample (FL-J117) and a healthy donor shown as median fold change, relative to unstimulated cells. On the archsinh scale, a FC of 1.75 corresponds to a difference of 1 log₁₀. Scatter plots of cytokine-induced phosphorylation in TILs from DLBCL, MCL, FL, and CLL and PBMC T cells from healthy donors. (B) IL-4–induced p-STAT6, (C) IL-10–induced p-STAT3, (D) IL-21–induced p-STAT3, and (E) IL-7 induced p-STAT5. Each dot represents one patient sample: DLBCL, n = 12; MCL, n = 19; FL, n = 14; CLL, n = 14; and healthy donor PBMCs (normal), n = 6. Significance between groups was determined by unpaired Mann-Whitney U test.