Induction of vesicle formation in a cell line derived from imaginal discs

Summary The ability of insect hemolymph to induce vesicles in a high passage insect cell line, IAL-TND1, is described. The factor responsible, designated VPA for ‘vesicle-promoting activity’, was determined to be heat sensitive, nondialyzable, and protease Type XIV sensitive but insensitive to trypsin digestion. In efforts to determine the source of VPA, hemolymph was collected from different developmental stages ofTrichoplusia ni, and certain tissues fromT. ni were cocultured with IAL-TND1 cells. Hemolymph from every developmental stage tested exhibited VPA although the effect was somewhat reduced in spinning-stage larvae. Additionally, several tissue, including fat body, tess, and imaginal discs, released VPA into the culture medium. Neural tissues and endocrine glands did not induce vesicle formation.