Lampreys have a sophisticated immune system with three types of white blood cell that resemble our B and T cells, new research shows.
Studying lampreys allows biologists to envision the evolutionary past, because they represent an early offshoot of the evolutionary tree, before sharks and fish.
Scientists have identified a type of white blood cell in lampreys analogous to the “gamma delta T cells” found in mammals, birds, and fish. Gamma delta T cells have specialized roles defending the integrity of the skin and intestines, among other functions.
The results are published in the journal Nature. The finding follows an earlier study showing that cells resembling two main types of white blood cells, B cells, and T cells, are present in lampreys.
In the human immune system, B cells can differentiate into antibody-secreting cells and can grab their targets directly, while T cells generally recognize their targets only through cell-to-cell contact.
“We have been able to define another lineage of T-like lymphocytes in lampreys,” says first author Masayuki Hirano, assistant professor of pathology and laboratory medicine at Emory University School of Medicine and the Emory Vaccine Center.
“This suggests that the genetic programs for all three lineages of white blood cells are very ancient.”
Hirano says the results indicate that distinct cells with functions that are similar to gamma delta T cells may have existed in the last common vertebrate ancestor, before jawed and jawless vertebrates diverged around 500 million years ago.
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