Generation of a cytoplasmic factor(s) that induced IgG secretion in nonstimulated cells was demonstrated in TRF-stimulated cells by using red cell-mediated microinjection. Injection of the cytoplasm from a TRF-stimulated B lymphoblastoid cell line (CESS) into nonstimulated cells induced an increase of IgG-producing cells. Injection of TRF itself did not induce an increase of IgG-producing cells. Active substance(s) in the cytoplasm were generated at 2 hr after TRF stimulation, and IgG-producing cells reached their maximum level at 40 hr after injection of the factor(s). DFP, but not actinomycin D, inhibited the generation of the cytoplasmic factor(s). The activity of the cytoplasmic factor(s) was not destroyed by RNase and not absorbed with anti-IgG. These results suggested that binding of TRF with its acceptors induced the generation of the cytoplasmic factor(s) involved in the transmission of TRF-mediated signals from membrane to nuclei.