Scientists working with Professor Bernd Kaina of the Institute of Toxicology at the Medical Center of Johannes Gutenberg University Mainz have demonstrated for the first time that certain cells circulating in human blood so-called monocytes are extremely sensitive to reactive oxygen species (ROS). They were also able to clarify the reason for this: ROS are aggressive forms of oxygen that are generated during states of "oxidative stress" and play a significant role in various diseases. However, ROS are also naturally produced by cells of the immune system, in particular by macrophages, in response to exposure to pathogens. Macrophages are, similar to dendritic cells, generated by monocytes, which happens when monocytes leave the blood stream and enter the tissue. The scientists show that both macrophages and dendritic cells are resistant to ROS, as opposed to their precursor cells, the monocytes. The Mainz team attributes this hypersensitivity of monocytes to multiple defects in DNA repair that are apparent in these cells. They assume that a sophisticated mechanism for regulating the immune response and preventing excessive ROS production is behind this phenomenon, which was observed for the very first time. Their work has been published in the leading scientific journal Proceedings of the National Academy of Sciences.
It is generally known that one of the undesirable effects of ionizing radiation and drugs used to treat cancer is an impairment of the immune system, which ceases to function properly. However, it is still unclear which immune system cells respond most sensitively following radio- and chemotherapy, and which cells are resistant. "This is the question we addressed in our current research project," explains Professor Dr. Bernd Kaina, Director of the Institute of Toxicology at the University Medical Center in Mainz. "We were able to demonstrate that human monocytes are hypersensitive to reactive oxygen species (ROS), while macropha
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Johannes Gutenberg Universitaet Mainz