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Immune functions that are traded for reproductive success



Immune functions that are traded for reproductive success

The female specimen of the deep-sea fish-fish species Melanocetus johnsonii is about 75 mm in size with a male growing on its abdomen 23.5 mm. Credit: Edith A. Wieder

Deep-sea fishing uses an incredible reproductive strategy. Tiny male dwarfs forever join the relatively giant females, grow their tissues and then establish general circulation. Thus, the male becomes completely dependent on the female for the supply of nutrients, such as a fetus developing in the womb, or a donor organ in a transplant patient. In fishing fish, this unusual phenomenon is called sexual parasitism and contributes to the reproductive success of these animals, which live in the vast expanse of the deep sea, where females and males are otherwise rare.

The constant attachment of males to females is an anatomical form of attachment that is otherwise unknown in nature, except for a rare phenomenon in genetically identical twins. The immune system is an extreme obstacle. It attacks foreign tissue as it destroys cells infected with pathogens. Simply point out the difficulties associated with organ transplantation in humans, which requires a careful comparison of donor and recipient tissue types with immunosuppressive drugs to ensure the long-term survival of organ transplantation. But how is it possible for fishermen to accept each other so easily when one can expect tissue rejection?

The phenomenon of sexual parasitism has posed a mystery that has existed for 1

00 years, since the first couple joined was discovered by an Icelandic fisheries biologist in 1920. Now scientists from Germany and the United States have solved this age-old mystery and reported their findings in a scientific journal Science.

Key functions of the immune system are eliminated

A few years ago, Thomas Boom, a physician and immunologist at the Max Planck Institute for Immunobiology and Epigenetics in Freiburg, Germany, and Theodor W. Pitsch, an ichthyologist and world-renowned fisheries expert at the University of Washington in Seattle, studied genome different species of fishing fish. They began by considering the structure of major histocompatibility antigens (MHCs). These molecules are on the surface of the body’s cells and signal the alarm of the immune system when the cells become infected with a virus or bacterium. To ensure that all pathogens are effectively recognized, MHC molecules are extremely variable, so that it is difficult to find the same or almost identical forms in any two individuals of the species. This feature underlies the problem of tissue coordination, which affects the transplantation of human organs and bone marrow.

Interestingly, researchers have found that fisheries that use permanent attachment are largely depleted in the genes encoding these MHC molecules, as if they have deprived themselves of immune recognition in favor of tissue synthesis. “In addition to this unusual constellation of MHC genes, we found that the function of killer T cells, which usually actively eliminate infected cells or attack foreign tissues during the process of organ rejection, was also severely blunted if not completely lost. These results hinted at the possibility that fishermen’s immune systems were very unusual among tens of thousands of vertebrate species, “said Jeremy Swann of MPI Immunobiology and Epigenetics and the study’s lead author.

Immune functions that are traded for reproductive success

Female Photocorynus spiniceps, 46 mm, with a 6.2 mm parasitic male attached to the back. Credit: Theodore W. Pitsch

Survival without acquired immune system

After these unexpected discoveries, scientists suspected that the reorganization of the immune system of fishermen may be even larger than expected. Indeed, further research has shown that antibodies, which are the second most powerful weapon in the arsenal of immune defense, are also absent in some species of fishing fish. “For humans, the combined loss of important immune systems observed in fishing fish will lead to fatal immunodeficiency,” said Thomas Boehm, MPI’s director of immunobiology and epigenetics and a leading scientist on the project.

However, fishermen are obviously able to survive without the necessary adaptive immune functions. Thus, the researchers concluded that animals use much more advanced natural remedies to protect against infections, an unexpected solution to the problem facing all living things. Indeed, until now it was believed that the partnership of acquired and innate immunity, when it was formed in evolution, could not be broken without serious consequences.

The immune system affects reproductive strategy

Thus, research shows that despite several hundred million years of a joint evolutionary partnership of innate and adaptive functions, vertebrates can survive without the adaptive immune systems previously thought to be indispensable. We hypothesize that as yet unknown evolutionary forces first cause changes in the immune system, which are then used to evolve sexual parasitism, “says Thomas Bem.

Interestingly, scientists believe that among their collection of fish, they even captured one species on the way to the development of sexual parasitism. “We think it’s great that an unusual way of reproducing has been invented several times independently in this group of fish,” said Ted Pitts of the University of Washington.

Although the details of improved innate immune systems in fishing fish have not yet been disclosed, the results of this study indicate potential strategies to enhance innate immune conditions in human patients suffering from congenital or acquired immune disorders. Thus, the scientific journey, which began with a vague observation aboard a fishing vessel in the middle of the Atlantic, unexpectedly opens up new avenues for the treatment of human immune disorders.


Detection of the immune system can end chronic rejection of organs


More information:
JB Swann el al., “Immunogenetics of sexual parasitism” Science (2020). science.sciencemag.org/lookup/… 1126 / science.aaz9445

Provided by the Max Planck Institute for Immunobiology and Epigenetics



Citation: Immune Functions Traded for Reproductive Success (2020, July 30), obtained July 30, 2020 from https://medicalxpress.com/news/2020-07-immune-functions-reproductive-success.html

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