AICD of lymphocytes with a Fas deficiency. AICD was compared with Fas sensitivity in one Fas-deficient ALPS-0 patient and one highly Fas-defective ALPS-I patient (P3). (A) CD95 expression (gray histograms) on day 9 TSST-1-activated T cells from one ALPS-0 patient (P7), one ALPS-I patient (P3), and control (one representative evaluation of 3). (B) TSST-1-activated T cells were restimulated with TSST-1 () or (C) CD3-activated T cells were restimulated with anti-CD3 (), and Fas-induced apoptosis was measured in T cells from each culture using agonistic anti-CD95 (). Means and SEM of are from 5 (B) and 3 (C) independent experiments. As for WT lymphocytes, the proportion of CD4⁺ T cells is not significantly different in anti-CD3-activated (53.2% ± 11.8%) versus TSST-1-activated (57.7% ± 13.8%) blasts (data not shown). (D) Apoptotic cell death was detected after 6 hours of stimulation of day 9 TSST-1-activated T cells from ALPS-0, ALPS-I, and healthy control donor (CT) after reactivation by soluble TSST-1 or CD95 cross-linking, using Annexin-V detection (x axis) and 7AAD exclusion dye (y axis). One representative experiment of 3. Numbers on plots are percentages of total cells.