"Discovering this capability goes completely against the long-accepted paradigm that the innate immune system which had evolved over a long period of time was 'perfect' in terms of meeting lower animals' needs," L. Courtney Smith, associate professor of Biological Sciences, said. "It was a big surprise, that continues to astound us," she added.
Like many "lower" animals such as insects, earth worms and others without an adaptive immune system (one that can make antibodies), a sea urchin's innate system seems to produce a wide diversity of proteins that probably can attack germs and protect the sea urchin from infection, a new study from Smith's lab shows.
She and her colleagues studied the purple sea urchin's response to a standard bacterial insult (a fragment of the cell wall called lipopolysaccharide, or LPS) using a genomic screen. They discovered that the sea urchin produces a surprisingly large number of proteins against LPS, and that many of them are similar but also show an unexpected amount of variability.
Possible role of 'innate immunity' higher up the evolutionary ladder
"We are beginning to understand how an animal without an adaptive immune system can still protect itself," Smith said, adding: "We're beginning to appreciate that the sea urchin may use genes that are different from antibodies and possibly even different mechanisms from humans and yet is still able to produce an array of proteins with lots of diversity."
The paper, "Macroarray analysis of coelomocyte gene expression in response to LPS in the sea urchin. Identification of unexpected immune diversity in an invertebrate," appears in Physiolo
Contact: Mayer Resnick
American Physiological Society