Immune challenges trigger cellular and humoral responses in adults of Pterostichus melas italicus (Coleoptera, Carabidae)

The present study focuses on the ability of Pterostichus melas italicus Dejean to mount cellular and humoralimmune responses against invading pathogens. Ultrastructural analyses revealed the presence offive morphologically distinct types of hemocytes: prohemocytes, plasmatocytes, granulocytes, oenocytoidsand macrophage-like cells. Differential hemocyte counts showed that plasmatocytes and granulocyteswere the most abundant circulating cell types and plasmatocytes exhibited phagocytic activityfollowing the latex bead immune challenge. Macrophage-like cells were recruited after the immunechallenge to remove exhausted phagocytizing cells, apoptotic cells and melanotic capsules formed toimmobilize the latex beads. Total hemocyte counts showed a significant reduction of hemocytes afterlatex bead treatment. Phenoloxidase (PO) assays revealed an increase of total PO in hemolymph afterimmune system activation with lipopolysaccharide (LPS). Moreover, the LPS-stimulated hemocytesshowed increased protein expression of inducible nitric oxide synthase, indicating that the cytotoxicaction of nitric oxide was engaged in this antimicrobial collaborative response. These results provide aknowledge base for further studies on the sensitivity of the P. melas italicus immune system to theenvironmental perturbation in order to evaluate the effect of chemicals on non-target species inagroecosystems.