RESPONSES OF NONIMMUNE LARVAE OF THE GYPSY-MOTH, LYMANTRIA-DISPAR, TO BACTERIA AND THE INFLUENCE OF TANNIC-ACID

The three types of hemocytes of nonimmune larval gypsy moth, Lymantria dispar, responding to bacteria included the plasmatocytes, granular cells, and coagulocytes. The hemolymph contained prophenoloxidase which required serine protease mediation to produce phenoloxidase. The extent of hemocyte activity against bacteria varied with the bacterial species and was not related to bacterial virulence. Avirulent Bacillus subtilis and virulent Xenorhabdus nematophilus were removed from the hemolymph by the hemocytes, whereas highly virulent Xenorhabdus luminescens was not. Both Xenorhabdus species damaged the hemocytes, reentered the hemolymph, and induced fat body disintegration. The possibility of bacterial cell-wall and cell-envelope carbohydrates influencing phenoloxidase production is presented. Lipopolysaccharides from X. nematophilus suppressed phenoloxidase activation but not phenoloxidase activity. Prophenoloxidase activated in vitro produced opsonins that accelerated the removal of X. nematophilus from the hemolymph in vivo. Selected hydrolyzable tannic acid concentrations reduced the ability of the larval hemocytes to remove X. nematophilus from the hemolymph. © 1992.