Every mammal studied so far builds its antibodies from a single set of genes, a rule that has held from mice to humans to whales. Vesper bats break it. Researchers at Tulane University, working with Stanford University and the Centers for Disease Control and Prevention, have found that more than 500 species of vesper bats carry two complete, separate copies of the genes that produce antibody heavy chains, an arrangement never documented in any other mammal and one that may help explain how bats live alongside viruses that would sicken almost anything else.
A Vesper Bat Genome With Two Antibody Systems
Antibodies are Y-shaped proteins assembled from two heavy protein chains and two light chains, and in every mammal examined before this study, the heavy chains come from a single genetic locus. Hannah Frank, an associate professor of ecology and evolutionary biology at Tulane and the study’s corresponding author, and her colleagues found that vesper bats instead carry two distinct heavy-chain gene systems. In the big brown bat, a common North American species used as the reference genome, one gene set contains 33 antibody genes while the second, previously unrecognized set contains 99 functional genes, giving the animal a far larger toolkit for generating different antibody shapes than researchers had assumed bats possessed.
A Single Ancient Duplication, Inherited Widely
After the initial discovery, the team examined the genomes of 26 additional bat species related to the big brown bat and found that nearly all of them carry the same doubled system, a pattern the researchers say points to one duplication event in a shared ancestor tens of millions of years ago rather than repeated independent occurrences. The finding places the origin of the second antibody locus deep in the evolutionary history of vesper bats, the largest bat family, which includes more than 500 species spread across every continent except Antarctica, according to the Tulane University release describing the work.
That a duplication this significant could persist undetected across so many species for tens of millions of years surprised even the researchers involved. Genome sequencing of bats has expanded rapidly in the past decade, yet the second heavy-chain locus had gone unrecognized in prior assemblies, likely because standard genome-annotation pipelines are built around the assumption, true in every other mammal studied, that only one heavy-chain gene cluster exists. Once the team knew what pattern to search for in the big brown bat, however, confirming its presence across two dozen additional vesper species took comparatively little time.
Filling In a Gap in Bat Immunology
Most prior research into how bats tolerate dangerous viruses has focused on the innate immune system, the body’s rapid, non-specific first line of defense, rather than the antibody-driven adaptive immune response. Frank said the new findings show why that adaptive side deserves far more attention than it has received. The doubled antibody-gene system does not by itself explain why bats function as reservoirs for viruses capable of causing severe disease in other species, but it reveals a level of immune complexity that was previously unknown and gives researchers, according to the phys.org account of the study, an entirely new avenue to investigate.
Why the Discovery Matters Beyond Bats
Vesper bats serve important ecological functions as insect predators, pollinators and seed dispersers, and their success as a family, spanning hundreds of species and nearly every landmass on Earth, has long puzzled biologists. At the same time, bats are natural hosts for viruses related to Ebola, Marburg, SARS and MERS, and understanding how they coexist with pathogens that are frequently lethal in other mammals could eventually inform strategies for reducing the risk that a virus jumps from bats into humans or livestock. The study, published in the journal Science Advances under the title “Immunoglobulin heavy chain locus duplication in bats,” frames the finding as a foundation for future work rather than a complete explanation, since researchers still do not know how the second gene set is regulated or whether both loci are active at the same time in a living bat.
An Argument for Studying Beyond Mice and Humans
Frank has argued that decades of immunology research built around humans and laboratory mice have left large gaps in scientists’ understanding of how immune systems can be organized, gaps that only become visible when a genuinely different species is examined closely. The vesper bat antibody system is one such gap: an arrangement of genes that had gone unnoticed for as long as researchers have been sequencing mammalian genomes, hiding in plain sight in one of the most numerous and widespread mammal families on the planet. The team’s next step is determining what role, if any, the extra gene set plays in the antibody responses bats mount against real infections.
Open Questions the Team Still Needs to Answer
Several basic questions remain unresolved even after the discovery. Researchers do not yet know whether both heavy-chain loci are switched on simultaneously in a given bat, whether one set is reserved for particular classes of pathogens while the other handles different threats, or whether the second locus is a more recent evolutionary addition still being fine-tuned by natural selection. Answering those questions will likely require sequencing antibody transcripts directly from living bats exposed to specific viruses, rather than relying solely on genome sequences, to see which genes are actually being read and translated into working antibodies during an active infection. Frank’s collaborators at Stanford and the CDC bring expertise in exactly that kind of functional antibody analysis, suggesting the next phase of the work is already taking shape.
This article was created with the assistance of AI and reviewed by an editor.
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