CD10 expression by H9 T cells after HIV infection (A), exposure to CD95 MoAb (C), and staurosporin or etoposide (D) for 24 hours. The cells induced into apoptosis by one of these treatments were separated from nonapoptotic cells based on their FSC and SSC. Apoptotic and CD10⁺ cells were observed in the same gate (gate 1). Apoptosis was measured by PI staining of permeabilized cells (A through D) or Annexin-V staining (D) and flow cytometry. (D) Only the percentage of CD10⁺ and apoptotic cells gated in 1 is reported. Control cells (B), incubated with medium or with an irrelevant MoAb, were composed of a homogeneous cell population that did not express CD10 and was not apoptotic. The inset in A shows the flow cytometry profile for gp120 staining to document the ongoing HIV infection of the cells in vitro.