These two traits are tenets of the vertebrate adaptive immune response, and their presence in invertebrate organisms suggests that the innate immune response is much more robust than previously thought.
While not of the same nature of the vertebrate response, it is now assumed that insects may possess mechanisms capable of generating some adaptive aspects in their immune response. The vertebrate adaptive immune response is able to respond to nearly any pathogen encountered through the process of somatic recombination. The insect innate immune response, however, has been shown to develop specificity against only a small fraction of pathogenic challenges 27 , This observation suggests at least two possibilities for the generation of specific and long-lasting protection in insects.
The first possibility is the existence of a set of evolutionarily acquired PRRs capable of mounting a specific response to certain types of pathogens that impose high selective pressure. This possibility would explain recent findings showing that insects activate an adaptive-like immune response, which is specific for certain species of insects and their respective pathogens.
It does not, however, provide a mechanism that would support the increased capacity of the insect host immune system after an initial infection.
The second possibility is the existence of a mechanism functioning similarly to somatic recombination in vertebrates This mechanism would exhibit diversity and potentially consist of components that are readily induced upon an immune challenge.
Such features would allow the system to specifically recognize different immune elicitors without encoding distinct receptors for each one.
In addition, the mechanism should be able to readily regulate the activation of immune effectors upon immune recognition. A few candidate molecules with the capacity for these features have been previously identified as possible components of a mechanism by which insects can demonstrate aspects of immune specificity. The Down syndrome cell adhesion molecule Dscam , a member of the immunoglobulin superfamily, contains four exons, which exhibit alternative splicing.
Alternative splicing of these exons produces three hypervariable Ig-domains, resulting in more than 18, isoforms in D. Further, a variable transmembrane-domain doubles the total number of possible isoforms to a staggering 38, These isoforms display different interaction specificity and provide a possible source of diversity for pathogen receptors.
The identification of various Dscam isoforms on the surface of immunocompetent cells further supported this theory. Therefore, Dscam is considered a potential candidate molecule for the regulation of adaptive aspects of the insect immune system In Anopheles gambiae , Dscam alternative splicing is triggered and controlled by challenge with various immune elicitors, and interfering with Dscam expression affects the phagocytosis and subsequent survival of the mosquitos in response to bacterial infection 30 Figure 2.
Interestingly, no changes in Dscam expression and splicing were found in D. Therefore, Dscam is an essential component of the innate immune system in some insect species, in which its hypervariability provides the host with a vast collection of pattern recognition molecules. Figure 2. Anopheles gambiae Down syndrome cell adhesion molecule AgDscam , a member of the Ig superfamily, generates semi-specific splice variants in response to various immune elicitors.
AgDscam blue bar contains four exons black squares , which exhibit alternative splicing, capable of producing 31, different isoforms represented in rows.
When mosquitoes are exposed to various bacteria, the repertoire of AgDscam splice variants not only differ but also contain a majority of variants capable of binding to the bacteria inside red square to which the insect is exposed. Despite prior belief that the insect innate immune response lacks specificity, the expanded use of insects in biomedical research as model organisms has prompted investigation into the intricacies of their response to various types of infection. Previous and recent research has shown that the insect immune response appears much more robust than previously considered.
These findings point out the ability of insects to exhibit a form of immune specificity. Further research has suggested that priming of the insect immune system is specific to the insect species and the type of pathogen.
The protective effect varies in specificity from providing protection against a wide range of pathogens or specifically against the pathogen to which the insect was initially exposed. In addition, lifelong persistence of immune protection in insects can be accompanied with highly specific recognition of the priming agent.
Previous research has also identified alternative splicing of Dscam in insects as a potential mechanism for generating specific, long-lasting immune responses Hypervariability in Dscam splice isoforms, paired with their expression patterns on the surface of immunocompetent cells and their ability to associate with bacteria 30 , suggests a mechanism similar to acquired immunity in vertebrates via somatic recombination.
While Dscam may not be implicated in promoting adaptive features of the innate immune response in insects, it is profoundly involved in the innate immune response in mosquitoes, but not in flies.
Despite these diverse, but certainly exciting, observations in the insect innate immune response, it is evident that the field of insect immunology is much more complex than previously envisioned. A great deal of the priming effect in insects and its impact on certain immune functions remains currently unexplored; therefore, future research using insect models promises a generation of thrilling information that will potentially uncover the relationship between immune priming and physiological responses in insects.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
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Microbes Infect —7. When foreign antigen shares similarity with the component of self, the antibodies generated could result in an autoimmune response. The focus of this review is to capture the contrast between specificity and promiscuity and the structural mechanisms employed by the antibodies to accomplish promiscuity, at the molecular level. The conundrum between the specificity of the immune system for foreign antigens on the one hand and the multi-reactivity of the antibody on the other has been addressed.
Antibody specificity in the context of the rapid evolution of the antigenic determinants and molecular mimicry displayed by antigens are also discussed. Sign In or Create an Account. Advanced Search. Sign In. Skip Nav Destination Article Navigation. Close mobile search navigation Article navigation. Volume , Issue 3. Previous Article Next Article.
All Issues. Cover Image Cover Image. Article Navigation. Review Article February 05 Antibody specificity and promiscuity Deepti Jain Deepti Jain. Correspondence: Deepti Jain deepti rcb. Salunke dinakar. This Site. All Rights Reserved. Date last modified: August 3, Wayne W.
Defense Mechanisms. Contents All Modules. Specificity of the Adaptive Immune System Each lymphocyte has only one type of epitope receptor, but pathogens have many potential antigenic molecules, each of which may have several epitopes.
Answer: This is accomplished through gene spicing. In most cases, a single gene encodes for a single protein.
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