A T-cell activation defect affecting the NF-κB pathway. (A) Proliferation of CD8⁺ T cells from P1 and P2 measured by carboxyfluorescein succinimidyl ester dilution after a 6-day stimulation of PBMC with PHA or anti–CD3/CD28-coated beads (black line). Unstimulated cells are represented by the gray area. Similar results were obtained for CD4⁺ T cells. Proliferation assays were performed twice with similar results. (B) Early T-cell activation as assessed by CD25/CD69 expression in P2 CD4⁺ T cells upon overnight stimulation of PBMC with the indicated stimuli. (C) Percentages of IL-2 and IFNγ producing CD45RO⁺ CD4⁺ T cells from a day control and P2 measured after a 4-hour stimulation of PBMC with PMA/ionomycin in the presence of Brefeldin A. Graphs represent data from 4 different healthy controls (open circles), the day control (open triangles), and the patient (black triangle). (D) Phosphorylation of p65 (left panel) and degradation of IκB (right panel) in T cells from P2 and a healthy control after stimulation with PMA/ionomycin for 15 minutes (black line) compared with medium control (gray area). All activation assays (B-D) were performed at least 3 times with similar results.