快猫短视频

A missing or dysfunctional part of the vertebrate immune system might explain why male seahorses and pipefishes can carry a pregnancy 鈥� and could possibly inspire novel treatments for immune-related diseases in humans and other animals.

at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, wanted to understand how seahorses and their relatives 鈥� members of the Syngnathidae fish family 鈥� became the only animals in the world known to have developed biological male pregnancy. So she and her colleagues sequenced the full genomes of 12 species of syngnathids, including some pipefish species in which males don鈥檛 actually become pregnant but instead carry fertilised eggs outside the body.

They found that certain major histocompatibility complex (MHC) genes involved in the immune system 鈥� such as MHC-2 genes, which have long been considered critical for recognising viruses, bacteria and other invaders 鈥� were either inactivated or missing in the species in which males become pregnant, but not in those where eggs are deposited into the water or are carried by the male outside the body.

The findings make some sense from an evolutionary perspective because active MHC-2 genes would make a pregnant male鈥檚 body attack embryos as invaders, says Roth, who presented her research at the .

But the results also create a mystery. Seahorses and their relatives thrive in 鈥渁n ocean of microbes鈥�, according to Roth. It now seems that they do so despite having inactive or absent MHC-2 genes.

Roth says this suggests that other animals with a backbone, including humans, could successfully fight off infections when MHC-2 pathway activity is hampered 鈥� for instance, by HIV infection.

鈥淲e used to think all vertebrates had [a] set immune system pathway, but now it seems that a lot more flexibility is possible,鈥� she says. 鈥淔or immunology, this is really revolutionising because, potentially, we could activate different pathways of the immune system and compensate for certain losses.鈥�

In other vertebrates, the pregnant female鈥檚 body temporarily downregulates MHC-2 gene function during early pregnancy, but only in the cells that touch the embryo, says team member Jamie Parker, also at GEOMAR. This stops the mother鈥檚 body from attacking the embryo while allowing her to maintain normal immune function in the rest of her body, thanks to continuously active MHC-2 genes.

However, the fact that seahorses and many pipefishes lack functional MHC-2 genes throughout their entire lives challenges current beliefs about how critical MHC-2 genes might be for fighting infections, says Roth. As such, if scientists could tap into the 鈥渋mmune system secrets鈥� of seahorses and understand how they survive without these MHC-2 genes, she thinks this might lead to new therapies for immune diseases.

鈥淰ertebrates鈥� immune system pathways might not be so stable after all,鈥� says Roth. 鈥淏y finding other pathways that could take over the role of MHC-2, for example, we might be better prepared for treating autoimmune diseases, or any kind of immune deficiency, like HIV. Depending on the needs, there鈥檚 potential for a lot more adaptation.鈥�

at the Free University of Berlin in Germany says the research is 鈥渧ery interesting鈥�, but applications beyond seahorses and pipefishes might be 鈥渁 bit too hypothetical鈥� at this point.

鈥淢aybe [these fish] live in an ecological niche that makes MHC-2 dispensable, but that doesn鈥檛 necessarily mean it鈥檚 dispensable for mammals living in quite a different environment,鈥� he says. Even so, such a theory 鈥渕akes sense鈥�, he adds, and he is keen to follow the research as it progresses.