CD3 mediates apoptosis of CTCL cells that are ingested by the APC, resulting in maturation to CD83⁺ DCs.

(A) Two-color cytofluorimetry of sequential samples obtained from the cocultured cells at 20 minutes after the addition of CD3 antibody demonstrate that 30% of the CTCL cells have become apoptotic as determined by their coexpression of CD3 (detected with a secondary antimouse antibody conjugated to FITC) and APO-PE (a marker of early apoptotic cells). Apoptosis of the CTCL cells increases at 35 minutes and begins to decline by 50 minutes. The number of DCs containing apoptotic material from the CTCL cells increased from 10% at 20 minutes to 30% of the APCs after overnight incubation, demonstrating maturation of the APC driven by phagocytosis of apoptotic tumor cells. (B) Immunofluorescent staining of sequential specimens from the CD3-treated cocultures demonstrates that DC maturation as measured by CD83 expression increases after overnight incubation with the apoptotic CTCL cells, as measured by flow cytometry.