Both T and B lymphocytes from WAS patients are more susceptible to apoptosis than T and B lymphocytes from normal individuals. Analysis of apoptosis was performed using TUNEL after staining with immunophenotyping cell surface markers. Four different WAS patients (no. 1 through 4) and 4 different normal controls were analyzed. (A) CD3⁺ T lymphocytes from WAS patients underwent apoptosis at a greater frequency than did normal lymphocytes. Statistical significance was shown after 96 hours of incubation in vitro (P = .0239) by an unbalanced repeated measures ANOVA. (B) WAS B lymphocytes (CD19⁺) are more susceptible to apoptosis than were normal B lymphocytes. The mean levels of apoptosis were clearly different, although, because of small cell numbers, the standard errors were too high to show statistical significance. The scales used in (A) and (B) are identical.