The protein syndecan-4 is found in the cell membrane of antigen presenting cells (APCs). These are immune cells that detect exogenous substances (antigens). They internalize them and migrate to the nearest lymph node, where they present them to other immune cells, namely T-cells. In this way they initiate an immune reaction that leads to sensitization to a particular antigen, like for example to a pollen allergen. It is upon renewed contact with this pollen allergen that the typical symptoms of allergic asthma arise. "In our study we were able to demonstrate that syndecan-4 plays a critical role in APC migration," says Polte. "When syndecan-4 is lacking, the APCs cannot find their way to the T-cells and consequently cannot activate them. As a result, the immune reaction cannot take place and the sensitization to a particular antigen ceases."
Through investigations at the University of Leipzig, the researchers were also able to show that syndecan-4 in the APCs also plays a central role in the inflammatory process of allergic asthma: the allergic asthma symptoms of mice improved when they were given antibodies against syndecan-4. "In principle, syndecan-4 would be a good starting point for new therapies," says Polte. "Since it exhibits various other functions in cell metabolism, potential side effects are still difficult to assess."
