Effects of CCL19 and CCL21 on CD4⁺ T-cell AICD. Naive CD4⁺ T cells were stimulated for 4 days with anti-CD3 and anti-CD28 mAbs with or without CCL19 (green bar) or CCL21 (red bar) in primary culture and were restimulated with anti-CD3 mAb and IL-2 (▪) or IL-2 alone (□) in secondary culture. After 2 days in the secondary culture, annexin V⁺PI⁻ apoptotic cells were detected on flow cytometer. (A-B) In primary culture, T cells were stimulated in the presence of various doses of chemokines (A) or with or without 10 ng/mL CCL19 in the presence or absence of 10 μg/mL anti-CCL19 mAb (B). (C) T cells stimulated in the primary culture without chemokine were restimulated with anti-CD3 mAb and IL-2 in the absence (blue bar) or presence of 100 ng/mL CCL19 (green bar) or CCL21 (red bar). The results are shown as mean ± SD in triplicate tests. Asterisks indicate significant differences by Student t test (P < .05). A representative result from 2 (A-B) or 3 (C) independent experiments is indicated. (D) Naive CD4⁺ T cells were prepared from gld FasL-deficient, lpr Fas-deficient, and WT mice, and treated as shown in panel A with 100 ng/mL CCL19 or CCL21.