Immunology: "The immunosensory system goes beyond the actual immune cells"

Interview with Prof. Gunther Hartmann

It guards the body but can become its enemy: the immune system defends us from intruding pathogens; it is also able to cause severe diseases if it falsely recognizes the body itself as a threat. Molecular receptors in the whole body enable the immune system to "sense" what happens within.


Photo: Gunther Hartmann

Prof. Gunther Hartmann; ©private talked to Prof. Gunther Hartmann from the University Hospital Bonn about the Bonn cluster of excellence “ImmunoSensation”. Hartmann and his colleagues there view the immune system as a sensory organ. It collects information about pathogens in the body and combines them to cause an immune response. The researchers can make use of this approach to treat autoimmune diseases. Professor Hartmann, what is the research topic of the “ImmunoSensation“ cluster of excellence?

Gunther Hartmann: The cluster perceives the immune system to be an immunosensory system, that is to say as another sensory organ that searches for pathogens or damages in the body using receptors. This system goes beyond the actual immune cells, since sensory receptors of the immunosensory system also exist in other somatic cells. It turned out that the immune system is also closely connected to other functional systems of the body, such as the metabolic or the nervous system. What disciplines are participating in this research project?

Hartmann: Two areas here at the University of Bonn are leading the way: the Faculty of Medicine as well as LIMES, Life and Medical Sciences, at the Faculty of Mathematics and Natural Sciences. The German Center for Neurodegenerative Diseases (DZNE) and the center of advanced european studies and research (caesar) are also participating in the cluster of excellence.

The departments of Immunology, Neurosciences and Mathematics of the University collaborate with the Department of Neurosciences at the DZNE and the Department of Biophysics and the Department of Molecular Sensory Systems at caesar. We also team up internationally with partners from the U.S., England, Ireland, Israel and Japan.
Photo: nervous system

The receptors of the immune system are present in the whole body. It is connected to the neural system as well, its information is analyzed in the immune organs; © Kene What does it mean exactly to view the immune system as a sensory organ? How is it connected with other body systems?

Hartmann: For most sensory organs, signal transmission takes place in the central nervous system. The signals are being integrated and analyzed here. The immune system is also connected to the nervous system, but its signals are being integrated in the immune organs themselves and not in the nervous system. The immune cells are generally mobile units. We also focus on how the entire information from these mobile units is being integrated, so that the correct immune response results from it: there needs to be a specific targeted immune response that does not damage one’s body, but prevents damage. In doing so, mechanisms of sterile inflammation, which take place independent from infection, bacteria or viruses, are an important topic of the cluster. Receptors that are located on immune and somatic cells are at the center of the immunosensory system. This is why non-immune cells also play a part in the immunosensory system. What role do receptors play in the pathogenesis of diseases or in their prevention, respectively?

Hartmann: There are different receptor families. One identifies viral nucleic acids, while another identifies bacteria-specific molecules. They discover the presence of invading microbes through the presence of specific molecules that do not exist in human beings and are thus able to initiate defense mechanisms against a disease early on. Other ligands also identify altered expressions and molecular abnormalities in the human organism, when those occur in large amounts for example or in altered molecular forms. However, a wrong identification of one’s own nucleic acids can trigger autoimmune diseases.
Photo: Antibodies und bacterium

Receptors are in the center of the research. They distinguish foreign and endoge-
nous molecules in the body. They collect information about possible threats and intruding pathogens; © Kaulitzki How does this view of the immune system differ from previous views?

Hartmann: Immunity research has experienced several waves of development. Until about 1965, we primarily dealt with the humoral immune system, which includes B cells and the antibodies they produce. Then we found out that T cells in turn regulate B cells. The special characteristic of both immune cell types, the B and T cells, is that they create new genes through the process of recombination during the course of a person’s life. This also creates new receptors, which are specifically geared towards certain new surface structures of bacteria or viruses. This is why we refer to an acquired immune system.

The acquired immune system however needs to be regulated to where an immune response is actually meant to be stimulated or not. The cells of the inherent immune system take over this function with dendritic cells leading the way. They recognize dangers to the organism through immunosensory receptors and activate T cells or induce tolerance. We now recognize both the receptors of the inherent immune system and the receptors of T and B cells with antibodies as components of the immunosensory system, since all receptors are highly specialized in recognizing threats and damages. What approaches arise from this to treat diseases?

Hartmann: Sterile inflammatory responses play an important role with certain widespread diseases such as atherosclerosis, neurodegeneration in Alzheimer’s disease or articular gout. A sterile inflammatory response is triggered in all these diseases. There are also different congenital sterile inflammatory diseases that often turn serious, for instance in the case of Muckle-Wells syndrome. These diseases can be treated well today, because we now understand the molecular mechanisms that are responsible for the overstimulation of the immune system by the body’s own molecules. By blocking the mechanisms that are involved in the inflammatory process, today we are able to balance the immunosensory system again and thus largely cure the inflammatory disease.

Cluster of excellence ImmunoSensation
Photo: Timo Roth; Copyright: B. Frommann

© B. Frommann

The interview was conducted by Timo Roth and translated by Elena O'Meara.