Insect immunity. 11. Simultaneous induction of antibacterial activity and selection synthesis of some hemolymph proteins in diapausing pupae of Hyalophora cecropia and Samia cynthia

Abstract

We have previously shown that pupae of the giant silkmoth Samia cynthia have a humoral antibacterial activity, which was induced by viable, nonpathogenic gram-negative bacteria (H. G. Boman et al., 1974). We show here that this activity was formed simultaneously with a selective incorporation of amino acids into eight polypeptide chains characterized by their electrophoretic behavior. If actinomycin D or cycloheximide were given at an early time, no antibacterial activity was found. If the inhibitors were given at the time of maximum activity, there was no effect with actinomycin D but a rapid decrease of the activity in the case of cycloheximide. The results imply that the messenger ribonucleic acid was stable, but that at least one protein component was turning over. Hemolymph from immunized pupae of another giant silkmoth, Hyalophora cecropia, was fractionated by ammonium sulfate precipitation. This procedure, together with the isotope distribution after co-electrophoresis in polyacrylamide gels, was used for comparing the response to injury and to different infections. Almost identical polypeptide patterns were obtained as a response to an infection with either viable Enterobacter cloacae or Bacillus subtilis. These patterns differed both qualitatively and quantitatively from the injury effect created by an injection as such. There was only a low antibacterial activity in each of the four fractions obtained by ammonium sulfate precipitation. However, a combination of three fractions restored a high killing activity. Fractionation of hemolymph from untreated pupae provided evidence for at least one preexisting factor which stimulated the killing of Escherichia coli. The osmotic pressure of the bacteria contributed to the antibacterial activity towards E. coli, but not towards B. subtilis. The killing of E. coli was inhibited by lipid A and, to a lesser extent, by an inhibitor of proteolytic enzymes. The similarities and differences with the mammalian complement system are discussed.

Gloverin, an Antibacterial Protein from the Immune Hemolymph of Hyalophora Pupae

“…In a study on selective synthesis of proteins in diapausing pupae of Hyalophora cecropia eight proteins were detected [22]. One of the proteins, P8, has a similar molecular mass and precipitate at the same concentration of ammonium sulphate as gloverin.…”

Bacteria‐induced protein P4 (hemolin) from Manduca sexta: A member of the immunoglobulin superfamily which can inhibit hemocyte aggregation

“…The mechanisms by which insect cells recognize nonself, triggering the defensive responses described above, are not understood. The induction of antibacterial proteins is nonspecific; all species of bacteria tested induce the same set of proteins [9,10]. Insect hemocytes phagocytose or adhere to nearly any foreign object, whether biotic or abiotic.…”

Implications of hemolin glycosylation and Ca2+‐binding on homophilic and cellular interactions

“…Hemolin was initially described as a soluble protein that is one of the main, newly synthesized immune proteins (previously known as P4) in Hyalophora cecropia following bacterial injection [4]. The purified protein did not exhibit antibacterial activity by itself [5], and further investigations of hemolin and its expression were carried out to gain some understanding of its role in the immune response [6].…”