IL-13 is crucial for triggering the cell growth of EBV-infected primary B cells and for maintaining the proliferation of LCLs. (A) B cells purified from 2 healthy donors were infected with EBV. Five days after infection, various doses of anti–IL-13 neutralizing antibodies (α-IL-13 Ab) or rabbit IgG were added. After 24 hours incubation, [³H]-thymidine was added, incubation was continued for a further 24 hours, and the amount of [³H]-thymidine incorporation was measured. (B) LCLs were cultured for 24 hours, and various doses of anti–IL-13 neutralizing antibodies or rabbit IgG were added. After 48 hours incubation, [³H]-thymidine was added, incubation continued for 18 hours, and the amount of [³H]-thymidine incorporation was measured.