Lymphocyte activation marker expression. Axillary lymph node lymphocytes from 5- and 12-week-old mice were assessed for expression of activation status molecules using multicolor flow cytometry. (A) Lymphocytes were gated first on CD3⁺B220⁻ (R1) and CD4 or CD8 to designate mature peripheral conventional T lymphocyte subsets, or on CD3⁺B220⁺ (R2) and then CD4⁻CD8⁻ DN T cells, or on CD3⁻B220⁺ (R3) B cells. (B) Expression of CD25, CD44, CD54, CD62L, CD69, and the chemokine receptor CCR7 was determined on each of these lymphocyte subsets. Data shown are histogram overlays with mean fluorescent intensity of individual histograms, indicating relative expression levels of each activation-status molecule on young (5-week-old) or older (12-week-old) B6.WT (black unfilled histogram), B6.TRAIL^−/− (red unfilled histogram), B6.gld/gld (unfilled green histogram), and B6.GT (blue unfilled histogram). Data are shown compared with B6.WT control Ig-stained cells (black filled histograms) for CD4⁺, CD8⁺, and B200⁺ cells, or B6.G control stained DN T cells (black filled histograms). Data shown are representative of repeated analysis of independently generated mouse cohorts.