Insect immunity and its signalling: an overview (original) (raw)
Related papers
Cellular and Molecular Mechanisms of Insect Immunity
Insect Physiology and Ecology, 2017
Multicellular organisms constantly encounter potentially harmful microorganisms. Although insects lack an adaptive immune system, they do have powerful means of fighting infections. Cellular responses involve phagocytosis of bacteria and encapsulation of parasites. In addition, insects can mount a humoral response against pathogens. This is characterized by the secretion of antimicrobial peptides into the hemolymph. Recognition of foreign pathogens involves specific receptors for sensing infection. These include peptidoglycan recognition proteins (PGRPs) and β-glucan recognition proteins (βGRPs). Engagement of these receptors starts signaling pathways that activate the genes that encode antimicrobial peptides. These pathways include the Toll, the Imd, and the JAK-STAT. This chapter describes the innate immunity of insects including both the cellular and humoral responses to bacteria, fungi, and parasites. In addition, recent advances in insect antivirus immune responses are discussed.
Biochemistry of Insect Immune System
2018
The multicellular organisms have been encountered by a diverse array of pathogens. In response to the foreign invaders, the insects has been reported to develop an immune system which is basically the interaction between the virulence of the pathogen and the defending capacity of the host insects. The immunity system in insects may be divided into basically innate and adaptive type immunity, but in insects only innate immunity is functional and the adaptive immunity is being absent in insects unlike mammals. Furthermore, the innate immunity is divided into cellular and humoral immunity in insects. Cellular immunity is being imparted by various haemocytes such as, plasmatocytes, granulocytes and oenocytoids and the humoral immunity is provided by various Anti Microbial Peptides (AMPs) which are produced by fatbodies. Behavioural immunity includes the avoidance and antiseptic behavior by the host insects towards the pathogens or the products of pathogens. The insect has to overcome a ...
Innate humoral immune defences in mammals and insects: The same, with differences ?
Virulence, 2018
The insect immune response demonstrates many similarities to the innate immune response of mammals and a wide range of insects is now employed to assess the virulence of pathogens and produce results comparable to those obtained using mammals. Many of the humoral responses in insects and mammals are similar (e.g. insect transglutaminases and human clotting factor XIIIa) however a number show distinct differences. For example in mammals, melanization plays a role in protection from solar radiation and in skin and hair pigmentation. In contrast, insect melanization acts as a defence mechanism in which the proPO system is activated upon pathogen invasion. Human and insect antimicrobial peptides share distinct structural and functional similarities, insects produce the majority of their AMPs from the fat body while mammals rely on production locally at the site of infection by epithelial/mucosal cells. Understanding the structure and function of the insect immune system and the similarities with the innate immune response of mammals will increase the attractiveness of using insects as in vivo models for studying hostpathogen interactions.
The Intestinal Immune Defense System in Insects
International Journal of Molecular Science , 2022
Over a long period of evolution, insects have developed unique intestinal defenses against invasion by foreign microorganisms, including physical defenses and immune responses. The physical defenses of the insect gut consist mainly of the peritrophic matrix (PM) and mucus layer, which are the first barriers to pathogens. Gut microbes also prevent the colonization of pathogens. Importantly, the immune-deficiency (Imd) pathways produce antimicrobial peptides to eliminate pathogens; mechanisms related to reactive oxygen species are another important pathway for insect intestinal immunity. The janus kinase/STAT signaling pathway is involved in intestinal immunity by producing bactericidal substances and regulating tissue repair. Melanization can produce many bactericidal active substances into the intestine; meanwhile, there are multiple responses in the intestine to fight against viral and parasitic infections. Furthermore, intestinal stem cells (ISCs) are also indispensable in intestinal immunity. Only the coordinated combination of the intestinal immune defense system and intestinal tissue renewal can effectively defend against pathogenic microorganisms.
Immunity in lepidopteran insects
Advances in experimental medicine and biology, 2010
Lepidopteran insects provide important model systems for innate immunity of insects, particularly for cell biology of hemocytes and biochemical analyses of plasma proteins. Caterpillars are also among the most serious agricultural pests, and understanding of their immune systems has potential practical significance. An early response to infection in lepidopteran larvae is the activation of hemocyte adhesion, leading to phagocytosis, nodule formation, or encapsulation. Plasmatocytes and granular cells are the hemocyte types involved in these responses. Infectious microorganisms are recognized by binding of hemolymph plasma proteins to microbial surface components. This "pattern recognition" triggers phagocytosis and nodule formation, activation of prophenoloxidase and melanization and the synthesis of antimicrobial proteins that are secreted into the hemolymph. Many hemolymph proteins that function in such innate immune responses of insects were first discovered in lepidopt...
Regulation of the Insect Immune Response: The Effect of Hemolin on Cellular Immune Mechanisms
Cellular Immunology, 1996
hours, generates a diverse set of broad-spectrum antibacterial proteins and peptides such as cecropins, at-Hemolin is a bacteria-inducible protein of the immutacins, defensins, and lysozymes (2). noglobulin superfamily identified in the silk moth Hya-Recently, unexpected similarities between the relophora cecropia. The role of this protein, in hemocyte spective innate immune defenses among insects and aggregation and phagocytosis, was studied in vitro. Hemocyte aggregation, stimulated by phorbol myris-vertebrates have been reported. Sun et al. (3) noticed tate acetate or lipopolysaccharide (LPS), was pre-that genes for the inducible antibacterial proteins in vented by hemolin in a dose-dependent fashion, but the giant silkmoth Hyalophora cecropia have a common hemolin did not disrupt aggregates once they had been upstream motif, similar to the binding site of NF-kB, a formed. Furthermore, hemolin was able to stimulate mammalian member of the Rel family of transcription phagocytic activity in both hemocytes and hemocytic factors. In mammals, NF-kB and other Rel proteins mbn-2 cells and this activity was enhanced by LPS. The play a central role in the transcriptional activation of enhanced phagocytosis produced by a combination of immune-related factors such as immunoglobulins, inhemolin and LPS was prevented by the protein kinase terleukins, adhesion molecules, and the proteins of the C (PKC) inhibitors staurosporine and H-7, and PKC acute-phase response (4). The same transcription facactivity in hemocyte crude extracts was enhanced by tors are also exploited by the human immunodeficiency hemolin and LPS, with the highest activity observed virus when it infiltrates the human immune system in the presence of both. Hemolin affected tyrosine (5). Sun and Faye (6) also showed that known inducers phosphorylation of hemocyte proteins, enhancing the of the insect antibacterial response, such as bacterial phosphorylation of two proteins of 20 and 30 kDa and lipopolysaccharides, activate a nuclear factor that preventing tyrosine phosphorylation of two proteins binds to the conserved kB-like motif. This factor also of 35 and 40 kDa. These results suggest that hemolin cross-reacts with antibodies against NF-kB. is involved in the regulation of the cellular immune The most significant and intriguing differences beresponses via a pathway that includes PKC activation tween the insect and vertebrate systems are that (i) and protein tyrosine phosphorylation. ᭧ 1996 Academic there is no evidence for clonal selection mechanisms in Press, Inc. insects and (ii) no immunoglobulins (Igs) have yet been observed in insects. Some insect proteins (fasciclin and neuroglian) which contain Ig-like domains play a role 47
Innate Immunity, 2014
Insects are capable of innate immune responses elicited after microbial infection. In this process, the receptor-mediated recognition of foreign bodies and the subsequent activation of immunocompetent cells lead to the synthesis ex novo of a peptide pool with antimicrobial activity. We investigated the inducible immune response of a coleopteran, Rhynchophorus ferrugineus, challenged with both Gram-negative and Gram-positive bacteria. After immunization, we evaluated the presence of antimicrobial peptides using either biochemical analyses or microbiological techniques. The antimicrobial properties of the newly synthesized protein pool, detectable in haemolymph fractions of low molecular mass, showed strong antibacterial activity against various bacterial strains (Escherichia coli, Pseudomonas sp. OX1, Bacillus subtilis and Micrococcus luteus). In addition to the preliminary study of the mechanism of action of the pool of antimicrobial peptides, we also investigated its effects on bacterial cell walls by means of fluorescence microscopy and scanning electron microscopy. The data suggest that the main effects seem to be directed at destabilizing and damaging the bacterial wall. This study provides data that help us to understand some aspects of the inducible innate immunity in a system model that lacks anticipatory responses. However, the weevil has finely tuned its defensive strategies to counteract effectively microbial infection.
Memory and Specificity in the Insect Immune System: Current Perspectives and Future Challenges
Frontiers in Immunology
The immune response of a host to a pathogen is typically described as either innate or adaptive. The innate form of the immune response is conserved across all organisms, including insects. Previous and recent research has focused on the nature of the insect immune system and the results imply that the innate immune response of insects is more robust and specific than previously thought. Priming of the insect innate immune system involves the exposure of insects to dead or a sublethal dose of microbes in order to elicit an initial response. Comparing subsequent infections in primed insects to non-primed individuals indicates that the insect innate immune response may possess some of the qualities of an adaptive immune system. Although some studies demonstrate that the protective effects of priming are due to a "loitering" innate immune response, others have presented more convincing elements of adaptivity. While an immune mechanism capable of producing the same degree of recognition specificity as seen in vertebrates has yet to be discovered in insects, a few interesting cases have been identified and discussed.
PLOS One, 2009
Recent ecological studies in invertebrates show that the outcome of an infection is dependent on the specific pairing of host and parasite. Such specificity contrasts the long-held view that invertebrate innate immunity depends on a broadspectrum recognition system. An important question is whether this specificity is due to the immune response rather than some other interplay between host and parasite genotypes. By measuring the expression of putative bumblebee homologues of antimicrobial peptides in response to infection by their gut trypanosome Crithidia bombi, we demonstrate that expression differences are associated with the specific interactions.