Exploring the diversity of animal immune systems

Humans rely on about 10 Toll-like receptors, proteins that help the immune system recognize infection. The purple sea urchin has more than 200. 

For researchers in Katherine Buckley’s laboratory in the College of Sciences and Mathematics, that difference offers a glimpse into how much remains unknown about animal immunity. 

“Of the roughly 7 million estimated animal species on the planet, we really only understand how immune responses work in the vertebrates, which consists of less than 100,000 species,” said Buckley, an associate professor in the Department of Biological Sciences. “We are only beginning to understand the many ways animals interact with microbes, both harmful and beneficial.” 

Comparative immunology seeks to broaden that understanding. 

Understanding immunity across species

The field looks beyond humans and laboratory mice to examine how immune systems work throughout the animal kingdom. 

That broader view helps scientists choose the right organism for the question at hand. Ferrets, for example, are useful for studying influenza. Zebrafish can help screen chemicals for harmful effects, while axolotls offer insight into limb regeneration. 

The field also has practical value. Research on species important to agriculture and aquaculture can support food security, while molecules discovered in other organisms may lead to new treatments or research tools. 

“In addition to gaining a broader understanding of biology, these molecules may provide novel sources of drug treatments or experimental tools,” Buckley said. “This is essentially biological exploring.” 

Buckley’s laboratory studies immune responses in sea urchins, sea stars and upside-down jellyfish. The team primarily examines how animals detect and destroy disease-causing microbes in the gut. Its research also explores how sea urchin immune cells develop, how the environment influences immune responses and how immune genes evolve. 

Much of the work involves Vibrio, a group of bacteria commonly found in marine environments. Some species cause cholera, food poisoning, severe wound infections or disease in fish. 

Because sea urchins share important biological features with humans, the research may also offer insights relevant to biomedical science. 

Tracing immune systems across time

Doctoral student Nick Kraieski studies Toll-like receptors, which are especially abundant in purple sea urchins. 

He examined the genomes of 27 marine invertebrates, including sea urchins, sea stars and acorn worms, to understand how these receptors evolved. Because these animals are more closely related to vertebrates than many other organisms, they provide useful points of comparison. 

“The broadest question is: how do the gene families, such as TLRs, that recognize microbesevolve,” Kraieski said. “By mapping out the evolutionary history of these genes, we can see how organisms respond to selective pressures from their pathogens.” 

His work revealed broad differences in the number of TLRs across species. 

 

“We still don’t know why some animals have many TLRs while others have few or none,” he said. 

Kraieski manually curated 2,372 gene predictions as part of the project, creating a vast dataset that posed another challenge when it came time to explain the findings clearly. 

He presented the analysis at the 17th North American Comparative Immunology meeting in Abbotsford, British Columbia, where his first conference talk earned the second-place student presentation award. 

“I’d never given a conference talk before NACIW 2026, so that alone made me feel nervous,” Kraieski said. “It wound up being not just my first conference talk, but my first conference award.” 

While Kraieski traces how immune genes have changed over time, doctoral student Tyler Smith studies how the immune system begins to take shape in sea urchin larvae. 

Because their embryos are easy to study, sea urchins offer a useful model for examining how specific genes guide immune-cell development. Smith’s broader goal is to understand how a single fertilized egg eventually produces the many cell types an adult animal needs. 

“By understanding these genetic patterns, we may better understand human development and how developmental processes drive the evolution of new features and species,” Smith said. 

Highlighting graduate research at Auburn

Smith and Kraieski were joined at the meeting by fellow Buckley laboratory doctoral students Amelia Williams and Jake Tatum. All four delivered 15-minute presentations on their doctoral research. 

“This was the first year that all four of them have been selected to give talks,” Buckley said. “It was also a good opportunity for the students to network and make connections that will hopefully lead to future jobs or postdoc positions.” 

Smith said the meeting allowed him to discuss his work, gather feedback and connect with researchers who could shape future collaborations. 

“The opportunity to share my research and learn from a wide variety of people has helped me greatly early in my career,” he said. 

The response to Kraieski’s presentation also gave him new confidence in the project. 

“It made me realize I’d told a really interesting story that others will want to hear,” he said. “I think what I love most about this process is the puzzle of detangling and describing large, messy gene families.” 

The meeting brought together researchers from the United States, Canada, Taiwan and France who study immune systems in animals ranging from corals and lampreys to whales, fish and opossums . 

“Having the four grad students from DBS be selected to present their work speaks very highly of our graduate program,” Buckley said.