Immune functions traded in for reproductive success


Immune functions traded in for reproductive success
A female specimen of the deep-sea anglerfish species Melanocetus johnsonii of about 75 mm in size with a 23.5 mm large male fused on her belly. Credit: Edith A. Widder

Deep-sea anglerfishes employ an incredible reproductive strategy. Tiny dwarfed males become permanently attached to relatively gigantic females, fuse their tissues and then establish a common blood circulation. In this way, the male becomes entirely dependent on the female for nutrient supply, like a developing fetus in the womb of her mother or a donor organ in a transplant patient. In anglerfishes, this unusual phenomenon is referred to as sexual parasitism and contributes to the reproductive success for these animals living in the vast space of the deep sea, where females and males otherwise rarely meet.

The permanent attachment of males to females represents a form of anatomical joining, which is otherwise unknown in nature except for the rare occurrence in genetically identical twins. The represents an extraordinary obstacle. It attacks foreign tissue as it would destroy cells infected by pathogens. Just witness the difficulties surrounding organ transplantation in humans, which requires the careful cross-matching of donor and recipient tissue types, together with immunosuppressive drugs, to ensure the long-term survival of the organ graft. But how is it possible anglerfishes accept each other so readily when tissue rejection might be expected?

The phenomenon of sexual parasitism has posed an enigma that has existed for 100 years, ever since the first attached couple was discovered by an Icelandic fisheries biologist in 1920. Now, scientists from Germany and the U.S. have solved this century-old conundrum and report their findings in the scientific journal Science.

Key functions of the immune system eliminated

A few years ago, Thomas Boehm, a and immunologist working at the Max Planck Institute of Immunobiology and Epigenetics in Freiburg, Germany, and Theodore W. Pietsch, an ichthyologist and a internationally renowned expert on anglerfishes working at the University of Washington in Seattle, set out to study the genomes of different anglerfish species. They began by looking at the structure of major histocompatibility (MHC) antigens. These molecules are found at the surface of the body’s cells and signal alarm to the immune system when the cells are infected by a virus or a bacterium. To make sure that all pathogens are efficiently recognized, the MHC molecules are extremely variable, so much so that it is hard to find identical or near-identical forms in any two individuals of a species. This feature is at the root of the tissue-matching problem that plagues human organ and bone marrow transplantation.

Interestingly, the researchers found that anglerfishes that use permanent attachment are largely depauperate in genes that encode these MHC molecules, as if they had done away with immune recognition in favor of tissue fusion. “Apart from this unusual constellation of MHC genes, we discovered that the function of killer T cells, which normally actively eliminate infected cells or attack foreign tissues during the organ rejection process, was also severely blunted if not lost entirely. These findings hinted at the possibility that the immune system of anglerfishes was very unusual among the tens of thousands of vertebrate species,” says Jeremy Swann from the MPI of Immunobiology and Epigenetics and first author of the study.

Immune functions traded in for reproductive success
Female of the species Photocorynus spiniceps, 46 mm, with a 6,2 mm parasitic male fused to her back. Credit: Theodore W. Pietsch

Survival without acquired immune facilities

After these unexpected discoveries, the scientists suspected that the reorganization of the immune system of anglerfishes might be even more extensive than expected. And indeed, further research indicated that antibodies, which are the second powerful weapon in the arsenal of immune defense, are also missing in some anglerfish species. “For humans, the combined loss of important immune facilities observed in anglerfishes would result in fatal immunodeficiency,” says Thomas Boehm, Director at the MPI of Immunobiology and Epigenetics and lead scientist of the project.

However, anglerfishes are obviously able to survive without essential adaptive immune functions. Thus, the researchers concluded that the animals use much improved innate facilities to defend themselves against infections, an unexpected solution to a problem confronting all living things. Indeed, until now, it was thought that a partnership of acquired and innate immunity, once it was formed in evolution, cannot be disentangled without severe consequences.

Immune system affects the reproductive strategy

The study thus shows that despite several hundred million years of co-evolutionary partnership of innate and adaptive functions, vertebrates can survive without the adaptive immune facilities previously considered to be irreplaceable. We assume that as-yet unknown evolutionary forces first drive changes in the immune system, which are then exploited for the evolution of sexual parasitism,” says Thomas Boehm.

Interestingly, the scientists believe that, among their collection of fishes, they have even captured one species en route to developing sexual parasitism. “We find it remarkable that the unusual mode of reproduction was invented several times independently in this group of fishes,” says Ted Pietsch from the University of Washington.

Although the details of the improved innate immune facilities in anglerfishes remain to be discovered, the results of this study point at potential strategies that enhance innate immune facilities in human patients who suffer the consequences of inborn or acquired impairment of immune facilities. Hence, the scientific journey that began with an obscure observation on board a fishing vessel out in the mid-Atlantic unexpectedly opens up new avenues for the treatment of immune disorders in humans.


Immune system discovery could end chronic organ rejection


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

Citation:
Immune functions traded in for reproductive success (2020, July 30)
retrieved 30 July 2020
from https://medicalxpress.com/news/2020-07-immune-functions-reproductive-success.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.



Related posts:

Algerian journalist Khaled Drareni handed three-year jail term
New approach to treating osteoarthritis advances
Mundspülungen könnten Corona-Übertragungsrisiko senken - Biermann Medizin
Beirut blast destroyed landmark 19th-century palace after painstaking restoration
Brain activity during psychological stress may predict chest pain in people with heart disease
Minimalinvasive Tests auf Lungenkrebs: Profile zirkulierender MicroRNA eignen sich bei symptomatisch...
Schools mull outdoor classes amid virus, ventilation worries
REM-Schlaf beeinflusst Essverhalten - Biermann Medizin
New treatment targets found for blinding retinal disease
Unkomplizierte Appendizitis bei Kindern: Antibiotika allein können auch zum Erfolg führen
Afghanistan peace talks near as Taliban says ready ‘within a week’ of prisoner release
Australia's internal borders to stay shut as Covid-19 daily toll reaches record
Konzentrierter zuhören mit geschlossenen Augen?
US health secretary meets Taiwan's president on breakthrough trip
Mechanismen für den Wiederaufbau der Myelinhülle entschlüsselt
Hong Kong media mogul and activist Jimmy Lai arrested for 'collusion with foreign powers'
Belarus president Lukashenko looks set to win re-election, prompting protests
Macron denounces 'cowardly' attack in Niger
US tops 5 million confirmed virus cases, to Europe's alarm
UK might stop official Covid death count over claims of 'exaggeration': Telegraph
Brazil makes grim milestone—100,000 deaths from COVID-19
New Zealand marks 100 days of virus elimination
US passes 5 million confirmed coronavirus cases
Masks in class? Many questions as Germans go back to school
Beirut protestors call for fall of government on second day of demonstrations
Protesters in Poland denounce arrests of LGBT activists
Six French tourists among eight killed by gunmen in Niger, local governor says
Brazil Reaches Milestone of More Than 100,000 Covid-19 Deaths and 3 Million Cases
Following One Contact Tracer on the Trail of the Virus
Europe swelters under a heatwave complicated by Covid-19 restrictions
Belarus opposition figures detained as Lukashenko faces challenge in presidential vote
Nagasaki marks 75th anniversary of atomic bombing
Afghanistan to release 400 'hard-core' Taliban as precondition to peace talks
Video of Uighur handcuffed to bed in quarantine centre refocuses attention on Chinese persecution
Lukashenko faces challenge in Belarus presidential vote, opposition figures detained
Trump signs orders extending economic relief for Americans amid pandemic
Brazil's coronavirus death toll surpasses 100,000
Macron hosts Trump for UN-backed virtual donor conference on Lebanon
Addition of sintilimab to pemetrexed and platinum improved progression-free survival
Phase 3 eXalt3 study shows significantly longer progression-free survival
CheckMate 743 shows that dual immunotherapy, nivolumab + ipilimumab
Brazil near 100,000 deaths from COVID-19
South Africa coronavirus deaths top 10,000: government
Schools face big virus test as students return to classroom
Bayern and Barcelona win places in the Champions League quarter-finals
Paris makes masks mandatory as virus toll crosses 722,000
NSD2 enzyme appears to prevent cellular senescence
Potentially predictive humoral immune response markers in COVID-19 patients
A Birthday at the Cemetery
Scientists look beyond antibodies in virus immunity hunt
Parents of College Students Worry, Should They Stay or Go?
Paris makes masks compulsory outdoors in busy areas from Monday
What to do when anxiety affects your sleep
C.D.C. Closes Some Offices Over Bacteria Discovery
Belarus opposition candidate's campaign manager detained before presidential vote
Venezuela sentences two American ex-soldiers to 20 years over failed ‘invasion’
Novel approach reduces SCA1 symptoms in animal model
Investigators recover 'black box' flight recorders from Air India crash
New test better predicts which babies will develop type 1 diabetes
Treatment option improves chances of survival for babies with rare cerebrovascular disorder
Beirut blast deals fresh blow to a government struggling with popular discontent
Modifying BACTRAC protocol provides first chance to study local leukocyte populations during stroke
UK calls on France to help crack down on migrants crossing English Channel
Big jump in Italy's daily new cases driven by travel
Deadly blast rocks military base in Somali capital Mogadishu
Second person dies from plague in China's Inner Mongolia
Lebanese to protest political leadership in aftermath of Beirut explosion
Coronavirus deaths in Latin America hit global high
Lyon hold off surging Ronaldo to beat Juventus, reach Champions League quarter-finals
Chinese fishing fleet raises fears on protected Galapagos Islands
Pinpointing the cells that keep the body's master circadian clock ticking
Genetic cause of congenital malformation discovered
Belarus opposition leader sees ‘longing for change’, but predicts rigged presidential vote
Three major scientific controversies about coronavirus
International probe into Beirut blast would ‘dilute the truth’
Children reveal what they really think of adults – in their own research paper
Mauritius in ‘environmental crisis’ as oil leak from grounded ship threatens coastline
New neural network helps doctors explain relapses of heart failure patients
Vaccines through microneedle skin patches
Sugar-based signature identifies T cells where HIV hides despite antiretroviral therapy
US schools reopen in virus hotspots
Latin America is now region with most COVID-19 deaths
Ireland announces local lockdowns as virus cases rise
A New Hampshire Poet Laureate Lifts Her City’s Covid-19 Advisories
Preston becomes latest UK city to face virus lockdown
Fewer Hip Fractures May Reflect a Drop in Smoking Rates
The governor of Beirut Marwan Abboud: 'This is like a genocide against the Lebanese people'
Cuomo clears New York schools statewide to open, carefully
Why the Coronavirus is More Likely to ‘Superspread’ Than the Flu
Forced evacuations as glacier the size of a football pitch threatens Italian valley
US reports show racial disparities in kids with COVID-19
Unidentified gunmen kill about 20 in attack on cattle market in eastern Burkina Faso
Need to Take the MCAT? You'll Still Have to Do It in Person
Indian serum institute to make 100 million virus vaccine doses
Covid-19 Live Updates: Global Tracker
Intranasal vaccine platform has potential for more effective vaccines, fewer side effects
At least 14 killed as Air India Express plane skids off runway in India
US imposes sanctions on Hong Kong leader Lam and other Chinese authorities
Newly discovered mutation could point to heart disease therapeutic target
Misinformation spreads after Lebanon blast: Missile, drone, nuclear warhead?

Leave a Reply

Your email address will not be published. Required fields are marked *

Next Post

Renada McGuire, Resilient Home Health Aide, Dies at 39

Thu Jul 30 , 2020
This obituary is part of a series about people who have died in the coronavirus pandemic. Read about others here. The challenges kept coming at Renada McGuire, and she kept rising to the occasion. Whether raising six children as a single mother, fighting through kidney and heart problems or learning […]