Proliferation of patient's (P1) CD4 T cells. PBMCs from the patient P1 and healthy controls (C) were labeled with CFSE and stimulated with plastic-bound anti-CD3 and anti-CD28 Abs for 72 hours. Cells were then stained with an allophycocyanin-labeled anti-CD4 Ab. The progressive dilution of the CFSE dye in daughter CD4 T-cell generations (“0” denotes undivided cells, “1” denotes cells after first division, etc) was analyzed by flow cytometry. The graph shows percentage (mean ± SD) of CD4 T cells in each generation. N = 4 experiments; *P < .05 (Mann-Whitney U test, pairwise comparison).