How Tiny Sea Creature Reveals Secrets of Immune Evolution

The tiny marine invertebrate’s genes shed new light on the immune system. According to a recent study done by experts at the University of Pittsburgh School of Medicine, the way a tiny marine invertebrate differentiates its own cells from competitors has striking similarities to the human immune system. The research, which was recently published in the journal Proceedings of the National Academy of Sciences, suggests that the building blocks of our immune system evolved much earlier than previously believed. This new information may help us better understand transplant rejection and, potentially, help develop new immunotherapies.  For decades, researchers have wondered whether self-recognition in a marine creature called Hydrating biologic carpus was akin to the processes that control whether a piece of skin can be successfully grafted from one person to another, said senior author Matthew Victors, Ph.D., assistant professor of surgery and immunology at the Thomas E. Start Transplantation Institute. “Our study shows for the first time that a special group of proteins called the immunoglobulin super family— which are important for adaptive immunity in mammals and other vertebrates — are found in such a distantly-related animal.” Sea anemones, corals, and jellyfish are all members of the same group as hydrating biology carpus. The animals, which have tube-like bodies and tentacles for catching prey, resemble miniature versions of wacky inflatable tube men dancing outside a car dealership. They grow in colonies and cover hermit crab shells like moss on a rock. “As colonies grow and compete for space on crab shells, they often bump into each other,” explained Victors, who is also associate director of the Center for Evolutionary Biology and Medicine in Pitt’s School of Medicine. “If two colonies recognize each other as self, they fuse together. But if they identify each other as non-self, the colonies fight by releasing harpoon-like structures from special cells.” Victors and his colleagues had previously identified two genes, Alr1 and Alr2, that were involved in Hydrating  fuse-or-fight system, but they hypothesized that there was more to the story. The study was funded by the National Science Foundation and the National Institutes of Health.  When compatible Hydrating biologic carpus colonies recognize each other as “self,” via ALR genes, they fuse together. Credit, A. L. et al., Proceedings of the National Academy of Sciences, 2022 Matthew Victor, Ph.D., assistant professor of surgery and immunology at the University of Pittsburgh Thomas E. Start Transplantation Institute and associate director of the Center for Evolutionary Biology and Medicine. Credit: Matthew When incompatible Hydrating biologic carpus colonies identify each other as non-self via ALR genes, they fight. As a result, the colony on the left started to grow over the colony on the right. Credit: Huene, A. L. et al., Proceedings of the National Academy of Sciences, 2022 The findings suggest that V-set domains evolved farther back in the evolutionary tree than previously believed. The animals, which have tube-like bodies and tentacles for catching prey, resemble miniature versions of wacky inflatable tube men dancing outside a car dealership. They grow in colonies and cover hermit crab shells like moss on a rock. “As colonies grow and compete for space on crab shells, they often bump into each other,” explained Victors, who is also associate director of the Center for Evolutionary Biology and Medicine in Pitt’s School of Medicine.