Skewed proportions of CD4⁺ CXCR5⁺ memory T-cell subsets in FL. (A) Proportions of CXCR5⁺ memory (CD45RA⁻) CD4⁺ T cells in the indicated tissues are expressed as the percentage of the total CD45RA⁻ memory T-cell population. (B) Shown are representative plots of healthy donor PBMCs, reactive TN, NLN, RLN, and FL defining CD4⁺CD45RA⁻CXCR5⁺ subsets defined by CD57 and CD25 expression. (C) Proportions of GC (CD57⁻CD25⁺), LZ (CD57⁺CD25⁻), OZ (CD57⁻CD25⁻), and the dual (dual, CD57⁺CD25⁺) CD4⁺CXCR5⁺ memory T-cell in the indicated tissues expressed as the percentage of the total CXCR5⁺CD45RA⁻ memory T-cell population. Triangles represent values for individual samples, and rectangles represent averages for each tissue type. *P < .05, **P < .01, and ***P < .001 compared with FL. (D) Quantitative RT-PCR analysis of sorted CXCR5⁺ T_FH subsets defined in panel B, from FL or NLN (BCL-6 or FOXP3 expression normalized to GAPDH). Color indicates the number of cycles more (red) or less (blue) than the GAPDH control. (E) Further characterizing the FL CD57⁺CD25⁺ dual population (first plot) into PD-1 and ICOS populations (second plot) defining a ICOS⁺PD-1^DIM and a ICOS⁺PD-1^BRIGHT population that are predominately FoxP3⁺ (third plot) and Bcl-6⁺ (forth plot), respectively. Shown is a representative analysis of one FL specimen, with similar results obtained when analyzing an additional 3 FL patient specimens (total n = 4).