Distribution of vector integration site in ex vivo T-cell clones. Distribution of integration sites, retrieved from T-cell clones isolated ex vivo from patient 2 (X, n = 22) and patient 3 (Y, n = 27), relative to gene density within a 1-Mbp window, compared with insertion sites retrieved from ex vivo and in vitro cell samples, as reported in Aiuti et al¹¹  (*). Each bar represents the percentage of integration sites within the corresponding gene density region.