Abstract
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.
Highlights
Host immune responses against microbial invaders are generally categorized as innate or adaptive
There is a possibility that in mealworms, as in honeybees, TRANSGENERATIONAL IMMUNE PRIMING (TgIP) modulates effectors that are synthesized during specific insect stages. Another comprehensive study has demonstrated that TgIP in M. sexta can generate different responses depending on the developmental stage of offspring [24]. These findings suggest that similar studies examining TgIP effects should always take into account all stages of offspring in both challenged and unchallenged insects
This observation is consistent for all three homologous secondary infections, which readily demonstrates that the insect innate immune system is able to differentiate between two very closely related bacterial species (Figure 1C)
Summary
Host immune responses against microbial invaders are generally categorized as innate or adaptive. Experiments involving priming of the bumblebee Bombus terrestris with a Gram-negative (P. fluorescens) or two closely related Gram-positive bacteria (Paenibacillus alvei and P. larvae) and subsequent challenging with either the same bacteria (homologous) or one of the two bacteria with which it had not been primed (heterologous) have shown that primed bees can survive a homologous secondary infection significantly better than a heterologous secondary infection [25] This observation is consistent for all three homologous secondary infections, which readily demonstrates that the insect innate immune system is able to differentiate between two very closely related bacterial species (Figure 1C). While not of the same nature of the vertebrate response, it is assumed that insects may possess mechanisms capable of generating some adaptive aspects in their immune response
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