RESUMO
Drosophila blood cells or haemocytes comprise three cell lineages, plasmatocytes, crystal cells and lamellocytes, involved in immune functions such as phagocytosis, melanisation and encapsulation. Transcriptional profiling of activities of distinct haemocyte populations and from naive or infected larvae, was performed to find genes contributing to haemocyte functions. Of the 13 000 genes represented on the microarray, over 2500 exhibited significantly enriched transcription in haemocytes. Among these were genes encoding integrins, peptidoglycan recognition proteins (PGRPs), scavenger receptors, lectins, cell adhesion molecules and serine proteases. One relevant outcome of this analysis was the gain of new insights into the lamellocyte encapsulation process. We showed that lamellocytes require betaPS integrin for encapsulation and that they transcribe one prophenoloxidase gene enabling them to produce the enzyme necessary for melanisation of the capsule. A second compelling observation was that following infection, the gene encoding the cytokine Spatzle was uniquely upregulated in haemocytes and not the fat body. This shows that Drosophila haemocytes produce a signal molecule ready to be activated through cleavage after pathogen recognition, informing distant tissues of infection.
Assuntos
Proteínas de Drosophila/metabolismo , Drosophila/genética , Hemócitos/metabolismo , Animais , Catecol Oxidase/genética , Catecol Oxidase/metabolismo , Linhagem da Célula , Drosophila/imunologia , Drosophila/microbiologia , Proteínas de Drosophila/genética , Precursores Enzimáticos/genética , Precursores Enzimáticos/metabolismo , Escherichia coli/patogenicidade , Corpo Adiposo/metabolismo , Corpo Adiposo/microbiologia , Perfilação da Expressão Gênica , Genoma , Hemócitos/imunologia , Hemócitos/microbiologia , Cadeias alfa de Integrinas , Integrinas/genética , Integrinas/metabolismo , Larva/genética , Larva/imunologia , Larva/microbiologia , Micrococcus luteus/patogenicidadeRESUMO
The Drosophila melanogaster host defense is complex but remarkably efficient. It is a multifaceted response to a variety of fungal, bacterial, and parasitic invaders. Current knowledge is discussed on recognition of infectious microorganisms and on the activation of intracellular signaling cascades that concur with the expression of numerous immune-responsive genes, among which, to date, the most prominent appear to encode potent antimicrobial peptides.
Assuntos
Drosophila melanogaster/imunologia , Imunidade Inata , Animais , Infecções Bacterianas/imunologia , Drosophila melanogaster/genética , Micoses/imunologia , Doenças Parasitárias em Animais/imunologia , Peptídeos/imunologia , Transdução de SinaisRESUMO
We have identified 242 Anopheles gambiae genes from 18 gene families implicated in innate immunity and have detected marked diversification relative to Drosophila melanogaster. Immune-related gene families involved in recognition, signal modulation, and effector systems show a marked deficit of orthologs and excessive gene expansions, possibly reflecting selection pressures from different pathogens encountered in these insects' very different life-styles. In contrast, the multifunctional Toll signal transduction pathway is substantially conserved, presumably because of counterselection for developmental stability. Representative expression profiles confirm that sequence diversification is accompanied by specific responses to different immune challenges. Alternative RNA splicing may also contribute to expansion of the immune repertoire.