Differential expression of PD-1 in CD4⁺ FL TILs and autologous PBMC CD4⁺ T cells and negative association with IL-4–induced p-STAT6. Immunophenotypic analyses of inhibitory receptors CTLA-4, BTLA, and PD-1 were performed in FL LN and autologous blood samples. (A) Representative FACS plot of TILs and peripheral blood T cells from a representative patient with FL. (B) Mean percentage of PD-1⁺ cells of CD4⁺ T cells. FL, n = 3; healthy donors, n = 3. (C) Mean percentage of BTLA⁺ cells of CD4⁺ T cells. FL, n = 3; normal, n = 3. (D) Scatter plot of IL-4–induced p-STAT6 in CD4⁺ T cells versus percentage of PD-1⁺ cells of CD4⁺ T cells in LNs and PBMCs from patients with FL and in tonsils and PBMCs from healthy donors. (E) Scatter plot of IL-4–induced p-STAT6 in CD4⁺ T cells versus percentage of BTLA⁺ cells of CD4⁺ T cells in LNs and PBMCs from patients with FL and in tonsils and PBMCs from healthy donors. Statistical difference between groups was determined by paired 2-tailed Student t test.