Bonn – People with multiple sclerosis often complain regarding stronger symptoms following consuming dairy products. Researchers from the Universities of Bonn and Erlangen-Nuremberg have now found a possible reason for this.
According to this, a protein in cow’s milk can trigger inflammation, which is directed once morest the “insulating layer” around the nerve cells. The study was able to demonstrate this connection in mice, but also found evidence of a similar mechanism in humans. The scientists recommend that certain groups of people affected should therefore avoid dairy products. The study has now been published in the journal PNAS.
The study was triggered by reports from MS patients: “We keep hearing from those affected that they feel worse if they eat milk, quark or yoghurt,” explains Stefanie Kürten from the Institute of Anatomy at the University Hospital Bonn. “We are interested in the cause of this connection.”
The professor of neuroanatomy is considered a recognized expert on multiple sclerosis. They started the study in 2018 at the University of Erlangen-Nuremberg. A year and a half ago she moved to Bonn, where she continued her work with her working group. “We injected mice with various proteins from cow’s milk,” she says. “So we wanted to find out if there is a component to which they react with symptoms of illness.”
In fact, the researchers found what they were looking for: when they gave the animals casein, an ingredient in cow’s milk, together with an effect enhancer, the mice then developed neurological disorders. The electron microscope showed that the insulating layer around the nerve fibers was damaged, the myelin. The fat-like substance prevents short circuits and also significantly accelerates the transmission of stimuli.
Perforated myelin sheath
In multiple sclerosis, the body’s immune system destroys the myelin sheath. The consequences range from discomfort and vision problems to movement disorders. In extreme cases, those affected end up in a wheelchair. In the mice, too, the insulating shell was massively perforated – apparently caused by the administration of casein. “We suspected the reason to be a misguided immune reaction, similar to that in MS patients,” explains Rittika Chunder, who is doing her habilitation in Prof. Kürten’s working group. “The body’s own defense actually attacks the casein, but also destroys proteins that are involved in the formation of the myelin.”
Such cross-reactivity can occur when two molecules are very similar, at least in part. The immune system then confuses them with one another, so to speak. “We compared the casein to different molecules that are important for the production of myelin,” says Chunder. “In doing so, we came across a protein called MAG. It looks very similar to casein in some areas – so much so that in the test animals, the antibodies once morest casein were also active once morest MAG.”
In the casein-treated mice, the body’s own defenses were also directed once morest MAG, which destabilizes the myelin. But to what extent can the results be extrapolated to people with MS? To answer this question, the researchers gave mouse casein antibodies to human brain tissue. In fact, they accumulated there on the cells that are responsible for myelin production in the brain.
Self-test for antibodies once morest casein
Certain white blood cells, the B cells, are responsible for the production of antibodies. According to the study, the B cells in the blood of MS patients respond particularly strongly to casein. Those affected probably developed an allergy to casein at some point through the consumption of milk. As soon as they eat fresh milk products, the immune system therefore produces large numbers of casein antibodies. These also damage the myelin sheath around nerve fibers due to cross-reactivity with MAG.
However, this only affects MS patients who are allergic to cow’s milk casein. “We are currently developing a self-test that people can use to check whether they have the appropriate antibodies,” says Kürten, who is also a member of the ImmunoSensation2 cluster of excellence. “At least this subgroup should refrain from consuming milk, yoghurt or quark.”
Cow’s milk may also increase the risk of developing MS in healthy people. Because casein can also trigger allergies in them – that’s probably not even that rare. Once such an immune response is established, cross-reactivity with the myelin can theoretically occur. However, this does not mean that hypersensitivity to casein will inevitably lead to multiple sclerosis, emphasizes the professor. There are probably other risk factors involved. Nevertheless, this connection is worrying, says Kürten: “According to studies, the MS numbers are increased in population groups in which a lot of cow’s milk is consumed.”
Participating institutions and funding:
In addition to the University of Bonn, the Friedrich-Alexander University of Erlangen-Nuremberg, the Klinikum St. Marien Amberg and the Stanford University School of Medicine were also involved. The study was supported by the German Research Foundation (DFG), the IZKF-ELAN program of the University of Erlangen-Nuremberg and private donors.
Publikation: Rittika Chunder et al.: Antibody cross-reactivity between casein and myelin-associated glycoprotein results in central nervous system demyelination with implications for the immunopathology of multiple sclerosis; PNAS; DOI: https://doi.org/10.1073/pnas.2117034119
