Immunity in lepidopteran insects (original) (raw)
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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.
Insect immunity and its signalling: an overview
The innate immunity is the immediate and sole response of invertebrates for the protection against foreign substances and pathogens. In insects, it relies on both humoral and cellular responses that are mediated via certain recognizing receptors and activation of several signalling pathways. Fat body and hemocytes are the origins for the production and secretion of antimicrobial agents and activators/regulators of cellular response, while cell mediated immunity in insects is performed by hemocytes. In the last years, research has focused on the mechanisms of microbial recognition and activation of intracellular signalling molecules in response to invaders. In this review, we summarize the mechanisms of the innate immunity in insects and refer to potential interactions between humoral and cellular responses, combined with the involving signalling pathways and their cross talk.
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 ...
Immune recognition in insects: conflicting effects of autologous plasma and serum
Journal of Comparative Physiology B, 1988
In insects, the mode of discrimination of self from non-self is poorly understood and the existence and role of opsonic-like factors is much debated. Using in vitro experiments with Locusta migra-tor& blood cells, some factors secreted by these cells into the incubation medium were found to help in recognition of heat-killed Xenorhabdus nematophilus (bacteria) and in their fixation on the haemocyte plasma membrane. These factors were ineffective in recognition and fixation of latex beads. They were present in the serum obtained after coagulation of the locust blood. In contrast, an important depressant effect was observed when plasma of the same insect species was added to the incubation medium. This inhibitory effect of plasma was observed with bacteria as well as with latex beads. It is concluded that haemocyte-derived humoral factors (=opsonic-like factors) act in the recognition of foreign particles by insect haemocytes. However, this recognition system requires a more thorough understanding, not only in the presence or absence of opsonic-like factors. When present, opsonic-like factors are controlled by plasma compounds which seem to depress their opsonic activity.
Journal of Insect Physiology, 1993
The effects of anti-haemocyte monoclonal antibodies on the cellular defence reactions of the wax moth, Gallericl mellonellu, were investigated. One of these monoclonal antibodies, termed GM, reacted with a ca 100 kDa protein only found associated with the granular haemocytes. Blocking of this protein with the monoclooal antibody caused a speciilc reduction in nodule formation, in the attachment of bacteria to granular haemocytes and in the adhesion of these cells to glass substrates. Other monoclonal antibodies with differing specificity had no effect on these processes. In contrast to the granule haemocytes, the adhesive and phagocytic properties of the plasmatocytes were apparently unaffected by the presence of the GM monoclonal antibody. The mechanism by which these monoclonal antibodies inhibit the reactions of the granular haemocytes is still unclear, although it is suggested that they act by blocking the activity of the 100 kDa protein during degranulation events of these cells following contact with foreign material. The similarity of this protein with other adhesion-promoting molecules is discussed. Monoclonal antibodies Haemocytes Haemocyte adhesion Phagocytosis Gafferia mefioneffa INTRODUCTION Unstable granule-containing haemocytes, often referred to as granular cells, granulocytes or coagulocytes/ cystocytes, are cells at the centre of the cellular defence reactions of insects and other arthropods (Ratcliffe et al., 1985). These cells, although only having limited phagocytic ability, are important in haemolymph coagulation (Rowley, 1977), in nodule formation (Ratcliffe and Gagen, 1977) and in the encapsulation of microbial and macrobial parasites (Schmit and Ratcliffe, 1977). They also contain agglutinins (Yeaton, 1983), lysozyme (Zachary and Hoffmann, 1974) and various components of the prophenoloxidase system (Schmit et al., 1977; Leonard et al., 1985a). Despite the great advances that have been made in the last two decades in our understanding of the role of the granular cells in the immune system of arthropods, many key questions remain unresolved. One of the most important of these is to determine the nature of the molecules produced by these cells that trigger immune recognition and stimulate the cellular defence reactivity of other blood cell types such as the plasmatocytes. Recently, we raised a number of monoclonal antibodies to the haemocytes of the wax moth, Galleria