Researchers have discovered that a type of tiny marine invertebrate has a blood-forming system and an immune system with remarkable similarities to humans. The findings could shed light on the evolution of human blood and immune systems and pave the way to new approaches to fighting human diseases, they say.
Tunicates are tiny organisms, about 3 millimeters long, that form flower-like colonies on rocks and other hard underwater surfaces. Scientists have long considered them to be the closest living relatives of vertebrates, a so-called ‘missing link’ between invertebrates and vertebrates (a group that includes humans).
In the new study, the researchers conducted a detailed microscopic analysis of blood and immune cells of tunicates. They identified blood stem cells in tunicates that are similar to those found in human bone marrow that are capable of dividing and specializing into different kinds of cells. They also found hundreds of genes that are similar to genes involved in blood formation in humans. In addition, the researchers also found that tunicates contain cells that are specialized to kill other cells in a way that is similar to certain cells in the human body that target tumor cells or cells infected by viruses. Analyzing cells in the tunicate could lead to new ways to fight cancer or organ rejection, the researchers suggest. Their study, partly supported by NHLBI, appeared in Nature.