Phenotypic characterization of FCRL3 ⁺ T cells. (A) Surface staining for CD25 expression in FCRL3⁺ and FCRL3⁻ CD4⁺ memory T cells. Cells were stimulated with plate-bound anti-CD3/CD28 for 48 h. Each dot represents one donor, N = 5. Mean ± SD, paired t test, two-tailed. From left to right: *P = 0.0174, *P = 0.015. (B) Live/Dead staining showing viability of sorted FCRL3⁺ and FCRL3⁻ CD4⁺ and CD8⁺ memory T cells, 3 days after activation. Each dot represents a different donor, N = 3–6. Mean ± SD, paired t test, two-tailed. From left to right: *P = 0.0369, *P = 0.0272. (C) BrdU incorporation assay to measure the proliferation of sorted FCRL3⁺ and FCRL3⁻ CD4⁺ and CD8⁺ memory T cells, 3 days after activation. Each dot represents a different donor, N = 3–4. Mean ± SD, paired t test, two-tailed. *P = 0.0226, **P = 0.0093. (D) Heatmaps showing the differential expression of selected genes from Fig. 3 A. (E) Surface staining for CXCR5 expression in FCRL3⁺ and FCRL3⁻ CD8⁺ memory T cells. Each dot represents one donor, N = 8. Mean ± SD, paired t test, two-tailed. *P = 0.0221.