Nematostella vectensis is an unglamorous little sea anemone that burrows into estuary mud and diverged from the human evolutionary line more than 600 million years ago — which is exactly what made it interesting to Ton Sharoni, a PhD candidate working with Professor Yehu Moran at the Hebrew University of Jerusalem, alongside collaborators at the University of North Carolina at Charlotte. If you want to understand how deep the roots of the immune system go, you study something distant enough that any shared trick had to evolve before humans and anemones existed as separate lineages at all.
Delete this anemone's "brake" gene, and its immune system doesn't speed up — it collapses entirely.
What they found, published in Nature Ecology & Evolution on June 26, 2026, was a protein they named CARDIB — CARD Inhibitor Binding protein — that structurally resembles MAVS, the molecule that switches on antiviral defenses in human cells. Every structural cue said it should function the same way. It doesn't. In the anemone, CARDIB suppresses the immune response rather than activating it. "Everything about CARDIB suggested it should function like MAVS," Moran said. "Instead, we discovered that it does the exact opposite."
A Brake That Turns Out to Be Essential
The stranger part came when the team used CRISPR to delete the CARDIB gene entirely and exposed the anemones to viral infection, expecting — logically — a stronger immune response with the brake removed. Instead, the animals lost the fight almost completely: viruses multiplied unchecked and the anemones' antiviral defenses failed to properly switch on. "Although CARDIB acts as a brake on the immune system under normal conditions, that brake turns out to be essential for mounting an effective antiviral response," Sharoni said. The team confirmed the effect held up outside the lab too, moving gene-edited anemones into open-air mesocosms of natural estuarine water in South Carolina, where CARDIB-lacking animals accumulated far more virus within days.
It's a reminder that "the immune system" isn't one blueprint nature arrived at once — it's a problem different lineages solved in genuinely different, sometimes inverted, ways. A brake that's required for the accelerator to work at all isn't how human biology handles this, and finding a working alternative logic in an anemone opens new questions about how many other solutions evolution quietly tried out along the way.
Image credit: Nematostella vectensis, the starlet sea anemone used in the study