Receptor-mediated internalization of huTR by CD30⁺lymphoma cells. Receptor mediated internalization was analyzed by confocal laser-scanning microscopy. CD30⁺ Karpas 299 (A-E) or CD30⁻ HD-MY-Z cells (F) were incubated with 25 μg/mL huTR (A,C,E,F) or anti-CD30 IgG (B,D) for 4 hours at 4°C (A,B) or 37°C (C-F). Goat anti-human IgG (Fc-specific) antibody FITC conjugate was used for detection (green). Cell nuclei were counter stained with DAPI (channel is shown in pink as false color). Laser-scanning microscopy was performed using a CLSM-510META with a Plan Neofluar 40×/1.3 oil DIC objective (Zeiss). The Argon laser 488-nm line was used for excitation of FITC and the UV laser with 364 nm was used for excitation of DAPI (beam splitter for UV/488 nm). Emitted light of FITC and DAPI was detected using the band pass filters 505 to 550 nm and 385 to 470 nm, respectively.