UVB-induced apoptosis of TC-1 cells and maturation of TC-1 antigen-loaded DCs. (A) TUNEL assay of UVB-treated and control TC-1 cells 24 hours post-irradiation. (B) DNA ladder assay of TC-1 cells 24 hours after irradiation with UVB light. (C) Flow cytometry analysis of annexin V in UVB-treated cells 24 hours post-irradiation. (D) Percentage of DCs that have engulfed tumor cells, as determined by flow cytometry. DCs were pulsed with cells killed by UVB. Apoptotic tumor cells were labeled with PKH26 prior to pulsing. DCs were stained with antibody against CD11c.