RESUMEN
Antimicrobial peptides accumulated in the hemolymph in response to infection are a key element of insect innate immunity. The involvement of the fat body and hemocytes in the antimicrobial peptide synthesis is widely acknowledged, although release of the peptides present in the hemolymph from the immune cells was not directly verified so far. Here, we studied the presence of antimicrobial peptides in the culture medium of fat body cells and hemocytes isolated from the blue blowfly Calliphora vicina using complex of liquid chromatography, mass spectrometry, and antimicrobial activity assays. Both fat body and hemocytes are shown to synthesize and release to culture medium defensin, cecropin, diptericins, and proline-rich peptides. The spectra of peptide antibiotics released by the fat body and hemocytes partially overlap. Thus, the results suggest that insect fat body and blood cells are capable of releasing mature antimicrobial peptides to the hemolymph. It is notable that the data obtained demonstrate dramatic difference in the functioning of insect antimicrobial peptides and their mammalian counterparts localized into blood cells' phagosomes where they exert their antibacterial activity.
Asunto(s)
Péptidos Catiónicos Antimicrobianos/biosíntesis , Péptidos Catiónicos Antimicrobianos/farmacología , Dípteros/citología , Cuerpo Adiposo/citología , Hemocitos/citología , Secuencia de Aminoácidos , Animales , Péptidos Catiónicos Antimicrobianos/química , Células Cultivadas , Fraccionamiento Químico , Cromatografía Líquida de Alta Presión , Medios de Cultivo/farmacología , Larva/citología , Larva/efectos de los fármacos , Linfocitos/citología , Linfocitos/efectos de los fármacos , Peso MolecularRESUMEN
The cytotoxic activity of hemocytes isolated from larvae of the blowfly Calliphora vicina was tested using human myelogenous leukemia K562 cells as target. Both single cell and cytotoxicity assays demonstrated that the hemocytes recognize the K562 cells as nonself, firmly attach to their surface and induce target destruction in a manner resembling the effect of mammalian cytotoxic lymphocytes. The cytotoxic activity increased dramatically in the course of larval metamorphosis and was considerably higher shortly before the onset of pupariation, compared to the activity of human peripheral blood or mouse spleen lymphocytes. In insects, the cytotoxic hemocytes may take part in defense against eukaryotic parasites and in the elimination of aberrant self cells, as well as in developmental processes such as metamorphosis.