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PubMed2005

Innate immunity.

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Child↗
PubMed2003

Adaptive innate immunity? Responsive-mode prophylaxis in the mealworm beetle, Tenebrio molitor.

A primary infection by a parasite may indicate a higher risk of being reinfected in the near future (since infection may indicate that enemies are becoming more abundant). Acquired immunity does not exist in invertebrates despite the fact that they also face increased risks of reinfection following primary exposure. However, when subjected to immune insult, insects can produce immune responses that persist for long enough to provide prophylaxis. Because these immune responses are costly, persistence must be maintained through a selective advantage. We tested for the possibility that these long-lasting immune responses provided increased resistance to later infections by experimentally mimicking a primary immune insult (pre-challenge) in larvae of the mealworm beetle, Tenebrio molitor, with lipopolysaccharides (LPS) prior to early or late exposure to spores of the entomopathogenic fungus Metarhizium anisopliae. We found that pre-challenged larvae produced a long-lasting antimicrobial response, which provided a survival benefit when the larvae were exposed to fungal infection. These results suggest that the observed response is functionally "adaptive".

Adaptation, Physiological↗
PubMed2004

The transcriptional innate immune response to flg22. Interplay and overlap with Avr gene-dependent defense responses and bacterial pathogenesis.

Animals and plants carry recognition systems to sense bacterial flagellin. Flagellin perception in Arabidopsis involves FLS2, a Leu-rich-repeat receptor kinase. We surveyed the early transcriptional response of Arabidopsis cell cultures and seedlings within 60 min of treatment with flg22, a peptide corresponding to the most conserved domain of flagellin. Using Affymetrix microarrays, approximately 3.0% of 8,200 genes displayed transcript level changes in flg22 elicited suspension cultures and seedlings. FLARE (Flagellin Rapidly Elicited) genes mostly encode signaling components, such as transcription factors, protein kinases/phosphatases, and proteins that regulate protein turnover. Approximately 80% of flg22-induced genes were also up-regulated in Arabidopsis seedlings treated with cycloheximide. This suggests that many FLARE genes are negatively regulated by rapidly turned-over repressor proteins. Twenty-one tobacco Avr9/Cf-9 rapidly elicited (ACRE) cDNA full-length sequences were used to search for their Arabidopsis orthologs (AtACRE). We identified either single or multiple putative orthologs for 17 ACRE genes. For 13 of these ACRE genes, at least one Arabidopsis ortholog was induced in flg22-elicited Arabidopsis suspension cells and seedlings. This result revealed a substantial overlap between the Arabidopsis flg22 response and the tobacco Avr9 race-specific defense response. We also compared FLARE gene sets and genes induced in basal or gene-for-gene interactions upon different Pseudomonas syringae treatments, and infer that Pseudomonas syringae pv tomato represses the flagellin-initiated defense response.

Arabidopsis↗
PubMed2004

Metabolic reprogramming in plant innate immunity: the contributions of phenylpropanoid and oxylipin pathways.

In their environment, plants interact with a multitude of living organisms and have to cope with a large variety of aggressions of biotic or abiotic origin. To survive, plants have acquired, during evolution, complex mechanisms to detect their aggressors and defend themselves. Receptors and signaling pathways that are involved in such interactions with the environment are just beginning to be uncovered. What has been known for several decades is the extraordinary variety of chemical compounds the plants are capable to synthesize, and many of these products are implicated in defense responses. The number of natural products occurring in plants may be estimated in the range of hundreds of thousands, but only a fraction have been fully characterized. Despite the great importance of these metabolites for plant and also for human health, our knowledge about their biosynthetic pathways and functions is still fragmentary. Recent progress has been made particularly for phenylpropanoid and oxylipin metabolism, which are emphasized in this review. Both pathways are involved in plant resistance at several levels: by providing building units of physical barriers against pathogen invasion, by synthesizing an array of antibiotic compounds, and by producing signals implicated in the mounting of plant resistance.

Arabidopsis↗
PubMed2004

Reassessing the role of defensin in the innate immune response of the mosquito, Aedes aegypti.

Defensin is the predominant inducible immune peptide in Aedes aegypti. In spite of its activity against Gram-positive bacteria in vitro, defensin expression is detected in mosquitoes inoculated with Gram-positive or negative bacteria, or with filarial worms. Defensin transcription and expression are dependent upon bacterial dose; however, translation is inconsistent with transcription because peptide is detectable only in mosquitoes inoculated with large doses. In vitro translation assays provide further evidence for post-transcriptional regulation of defensin. Clearance assays show that a majority of bacteria are cleared before defensin is detected. In gene silencing experiments, no significant difference in mortality was observed between defensin-deficient and control mosquitoes after bacteria inoculation. These studies suggest that defensin may have an alternative function in mosquito immunity.

Aedes↗
PubMed2006

Influence of major surgery on the mannan-binding lectin pathway of innate immunity.

The mannan-binding lectin (MBL) pathway of complement activation is important in host defence against pathogens and possibly against cancer. We investigated the effect of major surgery on two central components of the MBL pathway; MBL and the MBL-associated serine protease MASP-2, and for comparison also measured the interleukin (IL)-6 and C-reactive protein (CRP) levels. Serial blood samples were obtained from patients belonging to two different cohorts. Cohort 1 comprised 60 patients undergoing open or laparoscopic colectomy for benign disease (n = 12) or colon cancer (n = 48). Cohort 2 comprised 27 patients undergoing elective, open surgery for colorectal cancer, and was included in order to cover blood sampling between days 2 and 6. As expected, the surgical stress induced a marked acute phase response, as evidenced by a large increase in IL-6 (18-fold) and CRP (13-fold) levels with maximum at 12 h and 2 days, respectively. However, in both cohorts the levels of MBL and MBL-associated serine protease 2 (MASP-2) were largely unaffected, except for a minor but significant increase around day 8 in cohort 1. The preoperative levels of IL-6 and CRP were correlated significantly in both cohorts (r = 0.71, P < 0.0001 and r = 0.65, P = 0.005, respectively). Preoperative MASP-2 correlated with preoperative CRP (r = 0.59, P = 0.001) and IL-6 (r = 0.55, P = 0.02) in cohort 2 only. In contrast to the marked effects on the levels of IL-6 and CRP, the surgery influenced only marginally the two proteins of the MBL pathway.

Acute-Phase Proteins↗
PubMed2006

Comparative analysis of serine protease-related genes in the honey bee genome: possible involvement in embryonic development and innate immunity.

We have identified 44 serine protease (SP) and 13 serine protease homolog (SPH) genes in the genome of Apis mellifera. Most of these genes encode putative secreted proteins, but four SPs and three SPHs may associate with the plasma membrane via a transmembrane region. Clip domains represent the most abundant non-catalytic structural units in these SP-like proteins -12 SPs and six SPHs contain at least one clip domain. Some of the family members contain other modules for protein-protein interactions, including disulphide-stabilized structures (LDL(r)A, SRCR, frizzled, kringle, Sushi, Wonton and Pan/apple), carbohydrate-recognition domains (C-type lectin and chitin-binding), and other modules (such as zinc finger, CUB, coiled coil and Sina). Comparison of the sequences with those from Drosophila led to a proposed SP pathway for establishing the dorsoventral axis of honey bee embryos. Multiple sequence alignments revealed evolutionary relationships of honey bee SPs and SPHs with those in Drosophila melanogaster, Anopheles gambiae, and Manduca sexta. We identified homologs of D. melanogaster persephone, M. sexta HP14, PAP-1 and SPH-1. A. mellifera genome includes at least five genes for potential SP inhibitors (serpin-1 through -5) and three genes of SP putative substrates (prophenoloxidase, spätzle-1 and spätzle-2). Quantitative RT-PCR analyses showed an elevation in the mRNA levels of SP2, SP3, SP9, SP10, SPH41, SPH42, SP49, serpin-2, serpin-4, serpin-5, and spätzle-2 in adults after a microbial challenge. The SP41 and SP6 transcripts significantly increased after an injection of Paenibacillus larva, but there was no such increase after injection of saline or Escherichia coli. mRNA levels of most SPs and serpins significantly increased by 48 h after the pathogen infection in 1st instar larvae. On the contrary, SP1, SP3, SP19 and serpin-5 transcript levels reduced. These results, taken together, provide a framework for designing experimental studies of the roles of SPs and related proteins in embryonic development and immune responses of A. mellifera.

Amino Acid Sequence↗