Immune Systems in Insects and Vertebrates
The main topic of the text is the immune system of insects, including immune priming, transgenerational immunity, and the Dscam gene's role in pathogen recognition. It also discusses RNA interference as an antiviral defense and compares these mechanisms to vertebrates' adaptive immunity. The evolution and function of the acquired immune system in vertebrates are highlighted, showcasing the complexity and specificity of immune responses across different species.
See moreInsect Immune Priming and Transgenerational Immunity
Insects possess a unique form of immune memory known as immune priming, which allows them to mount a more robust defense against pathogens they have previously encountered. This is not due to adaptive immunity as seen in vertebrates, since insects lack specialized immune cells like B and T cells. Instead, their immune memory relies on innate immune mechanisms. Priming occurs when insects survive an infection or are exposed to non-lethal doses of pathogens. Their immune cells, called hemocytes, become better at recognizing and neutralizing the same pathogens in future encounters. Intriguingly, this enhanced immune response can be passed down to their progeny, a phenomenon known as transgenerational immune priming. This provides the offspring with a survival advantage against pathogens that their parents have encountered.The Dscam Gene and Immune Specificity in Insects
The Down syndrome cell adhesion molecule (Dscam) gene is pivotal in the insect immune system, contributing to its ability to specifically recognize pathogens. The Dscam gene can produce a vast diversity of protein isoforms through alternative splicing of its exons, which encode immunoglobulin domains. These different isoforms allow hemocytes to distinguish between a wide array of pathogens. When an insect encounters a pathogen, it generates Dscam isoforms that bind specifically to that pathogen. If the insect survives and the pathogen reappears, the presence of the matching Dscam isoforms enables a more effective immune response. This specificity is a key feature of the insect immune system, allowing it to adapt to the diverse microbial environment.RNA Interference as an Antiviral Defense in Insects
RNA interference (RNAi) is a crucial antiviral defense mechanism in insects, targeting viral RNA to prevent replication. The RNAi pathway involves several steps, starting with the recognition and cleavage of viral double-stranded RNA into small interfering RNAs (siRNAs). These siRNAs are incorporated into the Argonaute 2 (Ago2)-containing RNA-induced silencing complex (RISC), which then degrades viral RNA molecules that are complementary to the siRNA. Other RNAi pathways include the microRNA (miRNA) and PIWI-interacting RNA (piRNA) pathways, which also contribute to the regulation of gene expression and defense against viruses and transposable elements. These RNAi mechanisms are highly specific and form an integral part of the insect's immune defense.Adaptive Immunological Memory in Vertebrates
Vertebrates have a complex adaptive immune system characterized by the presence of memory B cells and T cells. These cells are capable of remembering specific antigens and mounting a rapid and potent response upon subsequent exposures. Immunological memory in vertebrates can be acquired actively through natural infection or vaccination, leading to long-lasting protection. Alternatively, passive immunity can be conferred temporarily through the transfer of antibodies, such as maternal antibodies passed to offspring. This adaptive immunity is a hallmark of the vertebrate immune system, providing a sophisticated and targeted response to a wide array of pathogens.Evolution and Function of the Acquired Immune System
The acquired, or adaptive, immune system is a relatively recent evolutionary development, first appearing in jawed vertebrates around 500 million years ago. It is characterized by the presence of highly specialized cells and molecules, such as lymphocytes, immunoglobulins, T cell receptors, and the major histocompatibility complex (MHC). These components are essential for the specific recognition of antigens. The diversity of the immune response is generated through a process known as V(D)J recombination, which allows for the production of a vast array of unique antigen receptors from a limited genetic repertoire. This enables the immune system to recognize and respond to an almost limitless variety of pathogens. The adaptive immune system operates in conjunction with the innate immune system, with each branch enhancing the effectiveness of the other.Want to create maps from your material?
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1
Insects have a form of immune memory called ______, which enhances their defense against familiar pathogens.
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2
Unlike vertebrates, insects do not have adaptive immunity because they lack ______ and ______ cells.
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3
Dscam gene function in insect immunity
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4
Role of immunoglobulin domains in Dscam
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5
Dscam isoform-pathogen re-encounter impact
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6
The RNAi defense begins by identifying and slicing viral ______ into small interfering RNAs.
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7
Small interfering RNAs (siRNAs) are part of the ______ complex, which degrades viral RNA matching the siRNA.
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8
The RNA-induced silencing complex that degrades viral RNA contains the protein ______.
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9
Apart from the siRNA pathway, insects also use ______ and ______ pathways as part of their RNAi defense mechanisms.
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10
RNAi mechanisms are highly specific and are a key component of an insect's ______ system.
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11
Types of adaptive immunity in vertebrates
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12
Role of memory B cells and T cells
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13
Duration of passive immunity
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14
Key elements of this immune system include ______, ______, and the ______, vital for specific antigen detection.
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15
The vast diversity in immune responses is due to ______, a process that creates numerous unique antigen receptors.
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