A new look at immune ageing

The thymus is the organ in which all T cells, a key white blood cell in our immune system, develop. The thymus shrinks with age, degenerating from a plump milky organ (just above the heart) to a ratty-looking fat-riddled vestige which barely produces any new T cells. This degeneration means that older persons are producing fewer and fewer T cells, contributing to the poor responses to vaccines and infections with age. Despite the importance of this process, there is a great debate in immunology over why the thymus gets worse with age, with some scientists pointing out the structural degeneration of the thymus itself, while others suggest that it is instead due to poorer function of the bone-marrow that sends stem cells to the thymus to be turned into T cells.

In a new study from the Autoimmune Genetics Laboratory, published in the European Journal of Immunology, we use a range of imaging and genetic techniques to address this key question. We undoubtly find the structural degeneration in the organ with age, but by comparing two mouse strains that have a thymus ageing at different rates, we find that the structural abnormalities do not actually limit production of T cells. Instead, it is the reduced function of the bone-marrow that leads to a reduction in new T cells. These results suggest that researchers looking into immune ageing direct their attention towards the bone-marrow, where rescuing stem cell production may allow even older persons to produce fresh T cells for a healthy life.

Data from Franckaert et al, European Journal of Immunology. The C57BL/6 mouse (top) has a thymus that ages slowly, while the FVB/N mouse (bottom) has a thymus that ages rapidly.

Jeffrey Modell Foundation supports Belgian research on primary immunodeficiency

For the first time the Jeffrey Modell Foundation is giving a research grant to a Belgian laboratory. The team of Adrian Liston from VIB-KU Leuven will use the grant to develop a gene therapy to cure children that suffer from IPEX syndrome, a rare and fatal autoimmune disorder in which the immune system attacks the body’s own tissues and organs. At the moment, the only successful therapy to treat the syndrome is a bone marrow transplantation, which is not available for all children.

 “This is a real chance for a cure”, said lead-researcher Adrian Liston. “The gene responsible for this disease was identified 13 years ago, but for the first time we may have learned enough about the basic biology to solve it. We should know within a year whether the gene therapy works in mice, after which we can move to patients at top speed.”

The Jeffrey Modell Foundation (JMF)

JMF is a global non-profit organization for patients who suffer from Primary Immunodeficiency (PI) and their relatives. The organization is devoted to early and precise diagnosis, meaningful treatments and, ultimately, cures. Through clinical and basic research, physician education, patient support, advocacy, public awareness and new-born screening they want to make a difference in the lives of patients with PI.

Vicki and Fred Modell established the Foundation in 1987, in memory of their son Jeffrey, who died at the age of fifteen from complications of PI. During the years, the foundation has created a network of the world’s leading expert immunologists. Two years ago the Child Immune Deficiencies Department of UZ Leuven was given the first certification as a "Jeffrey Modell Foundation Diagnostic and Research Center for Primary Immunodeficiencies” in Belgium.

IPEX and primary immunodeficiency (PI)

IPEX is an acronym for immune dysregulation, polyendocrinopathy (diseases affecting multiple endocrine glands), enteropathy (disorder of the intestines), and X-linked (pattern of inheritance).

IPEX Syndrome is classified as a primary immunodeficiency disorder. Primary immunodeficiencies are disorders in which part of the body's immune system is missing or does not function normally. IPEX is caused by mutations in the FOXP3 gene which lead to the dysfunction of regulatory T cells (a type of white blood cells).

IPEX syndrome is an autoimmune disorder, meaning that the immune system mistakenly attacks the body’s own tissues and organs. The syndrome is characterized by severe diarrhoea, dermatitis (inflammation of the skin), diabetes and severe, life-threatening infections. The disease only affects boys.

Current therapies still remain of partial efficacy. Immunosuppressive drugs are most commonly used, but they only delay the disease. Stem cell transplantation, when performed before severe autoimmunity develops, is currently the only effective cure. However transplantation is only a solution for those children with a compatible donor, unless a gene therapy option is available to correct the mutation in the patient’s own stem cells. 

Update on Wednesday, September 10, 2014 at 3:55PM by Adrian Liston

METRO.be

Amerikaanse beurs voor Vlaams onderzoek naar auto-immunziekte IPEX

Bio-Medicine

Jeffrey Modell Foundation supports Belgian research on primary immunodeficiency

News-medical.net

Belg ontvangt onderzoeksbeurs van Jeffrey Modell om behandelingsIPEX syndroom te helpen

MSN nieuws

Amerikaanse beurs voor Vlaams onderzoek naar auto-immunziekte IPEX

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Belgische Genforscher erhalten Geld einer US-Stiftung

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Jeffrey Modell Foundations supports Belgian research on primary immunodeficiency

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Amerikaanse beurs voor Vlaams onderzoek naar auto-immunziekte IPEX

New VIB group leader position available

The VIB is starting up a new group leader position in Hasselt University focused on autoimmunity research. The position will come with a €1.4 million start-up grant. Interested? Apply here.

Faculty position opening up in Leuven

See the details on NatureJobs

Women in Molecular Immunology

It is easy to discuss equality in science through anecodote. Just by spending most of my waking adult life on university campuses across three continents I am fairly confident in saying that sexual equality is better in biology and medicine than in chemistry or physics, is great at undergraduate level and lagging at professorial level, and is better in Australia than in Belgium. Much better than anecodote, though, is quantitative analysis, which is why I love this website. If you don't publish your research it is a hobby, not science, and a good publication record is the A to Z of career success for a scientist. This website collates data on authorship across time and across disciplines, at a global level, and assesses the participation of women. There are a few caveats: papers are only assessed if they are listed in the JSTOR database, and a gender is only assigned by first name analysis (using the US Social Security database as a reference, so it probably fails for first names not commonly used in the US). Still, it is an absolutely beautiful reference point.

There is an wealth of knowledge in this database, but my interest is in molecular immunology, so how are we performing? Well, the question kind of depends on "compared to what?" In 1991-2010, 29.7% of authors on molecular immunology papers were women. This is an improvement from 1971-1990 (23.9%), and a huge improvement from pre-history (being everything from 1970 and before, at 13.7%). It is also outstanding compared to fields such as mathematics, where women still only account for 10% authors (maths clearly has a problem with women; anyone who says the reverse is kidding themselves). But 29.7% is still a long way from 50%. Even among first authors (typically PhD students or post-docs), only 33.2% of molecular immunology authors were women, and among last authors (typically professors) only a dismal 15.4% were women. 

I've said before what I think the problem is (hint, it is men), but this database gives us a resource to see who is fixing the problem, and how fast, and who is content to live in the stone-age and try to do science with a 50% lobotomy. So many questions arise. Why has virology been more equal than immunology throughout the time period? I would love to see a break-down by country to know if this is a discipline-thing, or is a statistical quirk due to regional differences in sexism correlating by chance with regional differences in research focus.

Oh, and for the trivia-minded, within molecular biology the most equal area of research is heat shock proteins, while the most sexist is prostaglandins. In the entire database, the most female-dominated area of research is gender studies (57.8% female authors), while the most male-dominated area of research is a discipline of mathematics called Riemannian manifolds (99.3% male authors). Check it out.

Aire creates immune tolerance via an unconventional transcriptional mechanism

by Dina Danso-Abeam

The white blood cells of our immune system defend us from infection, a function which is coordinated by T cells. Immature T cells are formed with an ability to attack random targets (an adaptation to the rapid evolution of microbes), which means that by chance some targets are "self-targets" (normal proteins part of a healthy body). As a consequence, these "self-reactive" T cells can atatck the body, so it is critical to prevent them from causing autoimmune disease. To prevent autoimmunity, the immature T cells are screened in an organ called the thymus (located just above the heart), in order to ensure that all self-reactive T cells are eliminated.

The Aire gene plays an important part in eliminating self-raective T cells, by expressing genes that are normally restricted to specific organs (eg, insulin in the pancreas) in the thymus, providing full coverage for screening against self-reactivity. In patients that have mutations in the gene Aire, the thymus cannot provide full coverage of self-targets and fatal autoimmune disease develops. One of the mysteries of how Aire functions is its ability to express thousands of genes like insulin in the thymus. 

It has previously been shown that Aire is a transcription factor (meaning, it can bind DNA to activate genes and cause the expression of proteins) which can activate the expression of other transcription factors. We hypothesized that these secondary transcription factors might mediate the expression of the thousands of Aire-dependent genes like insulin; in effect, we predicted that Aire creates a cascade of transcription factors that results in the expression of thousands of genes.

In order to test this hypothesis, we investigated whether such a cascade regulates the transcription and tolerance of pancreas-specific antigens (e.g. insulin and glucagon) in the thymus. In the pancreas, Pdx1 is the key transcription factor which drives the expression of insulin. Interestingly both Pdx1 and insulin have been shown to be Aire-dependent in the thymus, so it was possible that Pdx1 was acting as a secondary transcription factor in the cascade by which Aire expresses insulin. Therefore we generated mice that specifically lack Pdx1 in the thymus.

By generating these mice, we found that expression of pancreatic-specific antigens such as insulin, needed Aire expression in the thymus, but did not need the transcription factor Pdx1. These results suggest that the broad tolerance that Aire creates in the thymus is not mediated by a conventional cascade of transcription factors, but rather relies on an unconventional transcriptional mechanism.  

This work will be published in a forthcoming issue of The European Journal of Immunology as:

Aire mediates thymic expression and tolerance of pancreatic antigens via an unconventional transcriptional mechanism

by Dina Danso-Abeam, Kim A Staats, Dean Franckaert, Ludo Van Den Bosch, Adrian Liston, Daniel H D Gray* and James Dooley*

Thymic involution: how a chance observation saved years of work

An interview with the VIB following the recent publication of our article:

The thymus is an organ crucial for the functioning of our immune system. During aging or infection the thymus can shrink severely, a process called involution. Although the mediators that trigger involution are known, the mechanisms regulating the sensitivity to their presence remained a mystery. Now, Smaragda Papadopoulou from the Bart De Strooper Lab and James Dooley from the Adrian Liston Lab describe in Nature Immunology a microRNA network that plays a key role. A chance observation kick-started the collaboration.

What did you discover about the regulation of thymic involution?

Adrian Liston: The main finding was the tight regulation by miR-29a over sensitivity to thymic involution. miR-29a serves to suppress the involution response, in effect "saving" involution for those situations where we really need it, such as during a major infection. Knowing what drives the reaction of the thymus is important, since it is the only place where T cells can develop. No thymus, no T cells, no infection prevention.

Is there an application side to those results?

For most of us, being born with a healthy thymus, we will generate enough T cells to last a life-time. Thymus involution during an infection is generally not a problem, nor the slow progressive involution that occurs from birth. The major problem is among the very elderly and with radiation/chemotherapy patients. If we could reverse thymic involution in those populations, we could rejuvenate their T cell population, providing them with a younger, more robust, immune system.

How did you go from studying regulatory T-cells to the regulation of thymic involution?

We have been interested in both the thymic epithelium and microRNA for years, so it was natural for us to look at what microRNA does in the thymic epithelium. As for thymic involution in particular, that was observation-driven. When we knocked out microRNA in the thymic epithelium using a Cre-Lox system, the main phenotype was chronic involution. But working out which microRNA is important was an enormous task. The big breakthrough for us was serendipitous. The Bart De Strooper Lab had generated a novel knockout mouse with a defect in one particular microRNA, miR-29a, to look at the neurophenotype. A conversation, a quick look and just by chance this microRNA turned out to be the one we needed for our lead. This enabled us to start a cross-disciplinary collaboration years before anyone else even knew there was a story there.

Did you use or design any new technologies for this research?

Far from it. The most important read-out in this work was the humble cell count. There are still enormous opportunities for high-level research using basic technologies. In this particular case the edge we had was a new mouse strain (the miR-29a knockout) and a new permutation of old mouse strains (Foxn1-Cre and Dicer-flox), but the rest was simply applying old techniques to a new problem. Immunology has so many fascinating questions that remain under-investigated that we spend our time working out which ones to tackle next, rather than designing new technology.

What’s the next step in your microRNA research?

MicroRNA are such interesting molecules. So tiny, they hold only a fraction of the information of a normal gene, yet they are incredibly versatile, affecting multiple completely unrelated targets in every cell type. We pretty much cracked the role of miR-29a in the thymic epithelium, but we are sure it is doing a lot more in other cell types of the immune system.

For the full research results see:

Aikaterini S. Papadopoulou#, James Dooley#*, Michelle A. Linterman, Wim Pierson, Olga Ucar, Bruno Kyewski, Saulius Zuklys, Georg A. Hollander, Patrick Matthys, Daniel H. Gray, Bart De Strooper and Adrian Liston. #Equal first authors. *Co-corresponding authors. 'The thymic epithelial microRNA network elevates the threshold for infection-associated thymic involution via miR-29a mediated suppression of the IFN-α receptor.' 2012. Nature Immunology. 13 p181.  Pubmed | Direct access

Generation of a family-specific virus through repeated human passage

Generation of a family-specific virus through repeated human passage

Hayden A M Liston¹, Lydia E Makaroff¹ and Adrian Liston ^1,2*
1 Sleepytown University, Brussels 1060, Belgium
² VIB, Leuven 3000, Belgium
*send correspondance to adrian.liston@gmail.com

Nature Junior 8(2) 103-7 

Background. Effective control over viral infection relies on the host carrying appropriate HLA alleles for viral antigen presentation. The explosive expansion of viruses like small-pox into previously isolated human populations demonstrates the potential for certain viral strains to have a disproportionate effect on particular racial groups. As yet, however, a virus with pathogenic potential restricted to the family level has not been identified. Objective. To generate a family-specific virus in an experimental setting, in order to test the feasibility of this occurrence in nature. Methods. A common cold virus was repeatedly passaged between two related individuals for six months. Mechanisms of transmission included frequent kisses, the placement of hands and feet into the mouth and in one instance direct vomiting into the mouth. Results. A single viral strain was propagated with the capacity to chronically infect both members of this family, while having seemingly non-pathological consequences upon exposure to unrelated individuals. The pathogenic loci are predicted to be a dominant HLA carried by both family members, as the experimental inoculation of a third individual, related to one family member but not the other, did not result in pathology. Conclusions. Generation of a family-specific virus is feasible through repeated experimental transfer between family members. A natural situation analogous to the experimental set-up used here would be the transmission that can occur between parents and young children with low levels of personal hygiene. The dominant activity of the HLA cluster in this infection suggests the generation of a regulatory T cell population which inhibits effective immunity against the family-specific virus.

Key Words: virus, horizontal transfer, HLA, human genetics, regulatory T cell.

Balance of the immune system determined by newly discovered T cells

From the VIB Press release: A newly discovered cell type helps to determine the balance of the immune system. The cells are derived from FoxP3(+) regulatory T cells, which recently have been demonstrated to suppress disease during transplantation. Nature Medicine and Blood, two high-ranking scientific journals, are publishing findings by the Autoimmune Genetics Laboratory about this discovery.

 

Innumerable people suffer from immune system disorders. If the immune system is overactive, it can result in allergies and autoimmune diseases such as Systemic lupus erythematosus (SLE). If the immune system is not active enough, infections or tumors occur. It is therefore essential to maintain the right balance.

 

The Autoimmune Genetics Laboratory is investigating a new type of cell that helps to maintain this balance. These ‘follicular regulatory T cells’ (Tfrs) suppress the process by which antibodies are produced during infections and SLE. The Tfrs themselves are daughter cells of FoxP3(+) T cells, key regulators of the immune system.

 

From lupus to cancer

In order to prevent disease the immune system needs to be in balance. If the system is too active, it produces antibodies against harmless substances, as is the case with allergies. An overactive immune system can even attack the body’s own tissues, causing autoimmune diseases such as lupus, rheumatism and diabetes. However, an insufficiently active immune system opens the way for rampant infections and tumors.

 

A complex network of regulatory cells is active to maintain this balance in our bodies. This must ensure that the immune system is sufficiently active and selective so that pathogenic intruders are recognized and eliminated in good time, but at the same time that it does not get out of control. This network of regulatory and activating cells is a long way from being fully unraveled. Dozens of researchers around the world are working to map this network.

 

This Tfr research is a joint collaboration between researchers from VIB-K.U.Leuven, the Australian National University (Aus) and the University of Cambridge (U.K.).

 

Publications

Linterman et al, Foxp3(+) follicular regulatory T cells control the germinal center response, Nat Med, 2011, doi:10.1038/nm.2425

 

Tian et al, Foxp3+ regulatory T cells exert asymmetric control over murine helper responses by inducing Th2 cell apoptosis, Blood, 2011, doi:10.1182/blood-2011-04-346056

The verdict on Andrew Wakefield: Fraud

In 1998 Andrew Wakefield published a paper which has severely damaged public health in the last ten years. Based on his observations of only twelve children, nine that he claimed had autism, and without a control group, he concluded that the measles/mumps/rubella vaccine caused autism. As a hypothesis, this was fine, unlikely, but not impossible. He saw nine children with autism, reported that their parents linked this onset with the MMR vaccine, and put it in the literature. Why on earth on underpowered observation like this made it into the Lancet is beyond me, but there is nothing wrong with even outlandish hypotheses being published in the scientific literature. Was it a real observation, or just an effect of a small sample size? Was it a causative link, or just due to coincidence in timing?

As with any controversial hypothesis, after this one was published a large number of good scientists went out and tested it. It was tested over and over and over again, and the results are conclusive - there is no link between the MMR vaccine and autism.

In itself, this was of no shame to Andrew Wakefield. Every creative scientist comes up with multiple hypotheses that end up being wrong. People publish hypotheses all the time, then disprove them themselves or have them disproven by others. If you can't admit being wrong, you can't do science, and it is in fact the mark of a good scientist to be able to generate hypotheses that others seek to knock down. Ten of the thirteen authors on the study were able to see the new data and renounce the hypothesis.

The shame to Andrew Wakefield is not that his hypothesis was wrong. No, the shame he has brought upon himself was by being unscientific, unscrupulous and unethical:

1. Firstly, Wakefield did not present his paper as a hypothesis generator, to be tested by independent scientists. Instead he went straight to the media and made the outrageous claim that his paper was evidence that the MMR vaccine should be stopped. This is not the way science or medicine works and was a conclusion unsupported by the data. Worst of all it was a conclusion that many parents without scientific training were tricked into believing. Vaccination rates for MMR went down (autism rates have remained unchanged) and children started dying again of easily preventable childhood diseases. A doctor does not see half a dozen children that developed leukemia after joining a football team and then hold a press conference telling parents that playing sports causes cancer in children, which is the direct equivalent of Wakefield's actions.
2. Secondly, it has now been conclusively demonstrated that his original data was fraudulent. Interviews with the parents of the original nine children with autism show that he faked much of the data of the time of onset, taking cases where autism started before the MMR vaccine and reversing the dates to suggest that the vaccine started the autism. Analysis of the medical records of these children show that as well as the timing being incorrect, many of the symptoms were simply faked and non-existent. The evidence on this charge alone makes Wakefield guilty of professional misconduct and criminal fraud.
3. Thirdly, unknown to the coauthors of the study and the parents of the children, Wakefield had a financial conflict of interest. Before the study had begun, Wakefield had been paid £435 643 to find a link between vaccines and disease as part of a lawsuit. Every scientist must disclose their financial interests in publication so that possible conflicts are known - Wakefield did not. If he had disclosed this to the press conferences the media may have been slightly more skeptical about his outlandish claims.

These last two issues, scientific misconduct and financial conflict of interest, are the reason why the paper was formally retracted by the Lancet. Studies that are wrong don't get retracted, they just get swamped by correct data and gradually forgotten. Instead, the retraction indicates that the Wakefield paper was fradulent and should never have been published in the first place. Likewise, the British General Medical Council investigated the matter and found that Wakefield "failed in his duties as a responsible consultant" and acted "dishonestly and irresponsibly", and thus struck him off the medical registry.

The worst part about this sorry affair is that it is still dampening down vaccination rates. Literally hundreds of studies, with a combined cohort size of a million children, have found no link between the MMR vaccine and autism, yet one fraudulent and retracted study of nine children is still talked about by parents. Some parents are withholding this lifesaving medical treatment from their children, and their good intentions do nothing to mitigate the fact that cases of measles and mumps are now more than 10 times more likely than they were in 1998, and confirmed deaths have resulted. And Andrew Wakefield, the discredited and disbarred doctor who started this all? Making big money in the US by selling fear to worried parents, and deadly disease to children who have no say in it at all.