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Immune functions traded for successful reproduction



Immune functions traded for successful reproduction

A female specimen of the deep ̵

1; sea marine species Melanocetus johnsonii, approximately 75 mm in size, the abdomen of which is fused to a male of 23.5 mm in size. Credit: Edith A. Widder

Deep-sea redfish use an incredible reproduction strategy. Tiny dwarf males are permanently attached to relatively giant females, fusing their tissues and creating a common blood circulation. In this way, the male becomes completely dependent on female nutrients, such as the developing fetus in the mother’s womb or an organ donor during transplantation. In sea bass, this unusual phenomenon is called sexual parasitism and contributes to the reproductive success of these animals, which live in a large part of deep-sea areas where females and males usually meet infrequently.

The constant attachment of males to females is a form of anatomical connection that is otherwise unknown, except in the rare case of genetically identical twins. The immune system is a tremendous hurdle. It attacks foreign tissues because it will destroy pathogen-infected cells. Just observe the difficulties of organ transplantation for people who need a careful combination of donor and recipient tissue types along with immunosuppressive drugs to ensure long-term survival of the organ transplant. But how is it possible that anglers take each other so easily when tissue rejection can be expected?

The phenomenon of sexual parasitism has caused a riddle that has existed for 100 years, since the 1920s. An Icelandic fisheries biologist has discovered the first attached pair. Scientists from Germany and the United States have now solved this century-old and report their findings in a scientific journal. Science.

The main functions of the immune system have been removed

A few years ago, Thomas Boehm, MD and immunologist at the Max Planck Institute for Immunobiology and Epigenetics in Freiburg, Germany, and Theodore W. Pietsch, an ichthyologist and internationally renowned angler expert at the University of Washington in Seattle . They began by examining the structure of major histocompatibility (MHC) antigens. These molecules are found on the surface of cells in the body and signal to the immune system when the cells are infected with a virus or bacterium. To make sure that all pathogens are effectively recognized, MHC molecules are extremely diverse, making it difficult to find identical or nearly identical forms in any two individuals of the species. This property is at the root of the tissue alignment problem that causes transplantation of human organs and bone marrow.

Interestingly, the researchers found that sea bass that use permanent attachment are part of the genes encoding these MHC molecules, as if they had abolished immune recognition in favor of tissue fusion. “In addition to this unusual constellation of MHC genes, we have learned that the function of killing T cells, which typically actively remove infected cells or attack foreign tissues during the organ rejection process, is also severely impaired, if not completely lost. These findings suggested the possibility that The immune system of redfish was very unusual among tens of thousands of vertebrate species, ”says Jeremy Swann of the MPI in Immunobiology and Epigenetics and the first author of the study.

Immune functions traded for successful reproduction

Female Photocorynus spiniceps, 46 mm, with a 6.2 mm male parasite, compressed on the back. Credit: Theodore W. Pietsch

Survival without acquired immune means

Following these unexpected discoveries, the researchers suspected that the rigging of the raccoon’s immune system could be even broader than expected. And indeed, further research has shown that antibodies to some marine marine species, which are the second most powerful weapon in the immune defense arsenal, are also absent. “In humans, the overall loss of important immune capabilities in raccoons can lead to fatal immunodeficiency,” says Tom Boehm, director of the MPI in Immunobiology and Epigenetics and lead researcher for the project.

However, redfish are clearly able to survive without essential adaptive immune functions. Thus, the researchers concluded that animals use significantly improved innate means to protect themselves from infections – an unexpected solution to a problem faced by all living things. Indeed, until now, it has been thought that the partnership between acquired and innate immunity formed during evolution cannot be separated without severe consequences.

The immune system influences the reproductive strategy

Thus, the study shows that despite a partnership of innate and adaptive functions for several hundred million years, vertebrates can survive without adaptive immune measures that were previously considered irreplaceable. We believe that the as yet unknown forces of evolution primarily drive changes in the immune system, which are then exploited for the evolution of sexual parasitism, ”says Thomas Boehm.

Interestingly, scientists believe that among their fish collection, they even caught one species on the way to sexual parasitism. “We find it amazing that an unusual method of reproduction has been self-invented several times in this group of fish,” says Ted Pietsch of the University of Washington.

Although information on an improved innate guinea pig immune system remains to be learned, the results of this study indicate possible strategies that strengthen the innate immune system in people suffering from congenital or acquired immune system disorders. Thus, the scientific voyage, beginning with vague observations on a fishing vessel in the middle of the Atlantic, unexpectedly opens up new possibilities for the treatment of immune disorders in humans.


The discovery of the immune system can result in chronic organ rejection


More information:
JB Swann et al., Immunogenetics of Sexual Parasitism. Science (2020). science.sciencemag.org/lookup/… 1126 / science.aaz9445

Presented by Max Planck Institute for Immunobiology and Epigenetics



Citation: Immune Functions Traded for Successful Reproduction (July 30, 2020), Obtained from 2020 July 30 From https://medicalxpress.com/news/2020-07-immune-functions-reproductive-success.html

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