Sistema imune inato em Melípona scutellaris (Hymenoptera, Apidae, Meliponini)

Abstract

CHAPTER II: Infection in insects stimulates a complex defensive response. Recognition of pathogens may be accomplished by plasma or hemocyte proteins that bind specifically to bacterial or fungal polysaccharides. Several morphologically distinct hemocyte cell types cooperate in the immune response. Hemocytes attach to invading organisms and then isolate them by phagocytosis, by trapping them in hemocyte aggregates called nodules, or by forming an organized multicellular capsule around large parasites. In the current investigation the cellular population in the hemolymph third instar larvae of M. scutellaris has been characterized by means of light microscopy analysis and phagocytosis assays were performed in vivo by injection of 0,5μm fluorescence beads in order to identify the hemocyte types involved in phagocytosis. Four morphotypes of circulating hemocytes were found in 3rd instar larvae: prohemocytes, plasmatocytes, granulocytes and oenocytoids. The results presented plasmatocytes and granulocytes involved in phagocytic response of foreign particles in 3rd instar larvae of M. scutellaris. CHAPTER III: Insects are continuously exposed to potentially pathogenic microorganisms and eukaryotic parasites, but only a few encounters result in infection. Insects possess a complex and efficient system of biological defense against pathogens and parasites. This system involves the following: the integument and gut as physical barriers to infection, coordinated responses of several subpopulations of hemocytes when these barriers are breached, and the induced synthesis of antimicrobial peptides and proteins, primarily by the fat body. The purpose in the present study was to verify a Toll receptor (MsToll) expression in Melipona scutellaris. By semiquantitative RT-PCR we evaluate the MsToll levels at different development stages and in different M. scutellaris workers tissues. The MsToll expression in the immune response was evaluated by real time RT-PCR in workers infected with Escherichia coli (gram-negative). Our data showed lower MsToll expression in the larval stage compared with other development stages. The specific tissue analysis showed that its expression in intestine was significantly higher compared with other tissues analyzed. Furthermore, the MsToll levels in innate immune response of M. scutellaris showed four folds enhanced in bees infected with E. coli compared with control.