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Immune and circulatory systems are integrated in insects

New understanding of how insects fight, succumb, or transmit infections

Researchers have discovered that the immune and circulatory systems are integrated in insects.

December 16, 2020

Biologists have found solid evidence that among the insects of life, the relationship between the immune and circulatory systems is consistent. The discovery will help researchers understand how insects – including the relatively few that transmit disease to animals or agricultural crops – fight, succumb, or transmit infections.

The research, funded by the US National Science Foundation, was published in the journal Science Advances.

Julian Hillyer from Vanderbilt University studies how mosquitoes fight infections and circulate their blood – two processes that influence each other. When mosquito immune cells detect a pathogen, they migrate to the heart and destroy the infection when the circulatory system brings them there. The process is similar to how human immune cells migrate to areas of high blood flow such as the spleen and lymph nodes to fight infection.

Together with the researcher Yan Yan, Hillyer set out to investigate whether this process occurs in other insects. Researchers analyzed 68 species of insects from 51 families representing 16 orders – a significant amount – to get a true cross-section of insect biodiversity.

Among the insects examined were the malaria mosquito and the yellow fever mosquito – two species that are as evolutionarily different as humans and whales – and bedbugs. Most of the insects were collected in the wild in various state parks.

“When we took the insects to the lab, we used advanced microscopy techniques to look for recognizable patterns between their hearts and immune responses to infection,” said Yan. “We have indeed seen the same behavior in most insects, which clearly showed us that the way they fight infection is dramatically affected by the way their circulatory systems work.”

Insects carry out tasks that are critical for survival, explained Hillyer, such as pollinating plants, aerating the soil and circulating nutrients through the ecosystem. “That makes the complete elimination of insects like mosquitoes unhealthy to the planet, although they are also responsible for spreading deadly diseases to humans and plants. Now we have a clear picture of how insects’ immune and circulatory systems work together, researchers can Develop techniques to modify their immune systems to prevent the transmission of diseases from insects to mammals or plants. “

Building on this work and previous research on the mechanics and timing of immune and circulatory processes in mosquitoes, the researchers are investigating the molecular mechanisms that cause the immune cell to get to the heart and how a disruption of this mechanism affects the insect .

“With climate change, insect areas are increasing,” says Joanna Shisler, program director in NSF’s Integrative Organizational Systems division. “These include insects such as mosquitoes and ticks, which carry microbes that are harmful to humans. If we know how insects fight infections, we can selectively control the spread of pathogens to humans.”

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