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Birgit Sawitzki finds every part of the immune system exciting, but her “favorite cells” happen to be T cells. “T cells are the conductors of the whole orchestra of immune cells and signaling molecules,” she enthuses. “T helper cells make it possible to develop a targeted defense using tailored antibodies, T killer cells specifically destroy infected or malignant cells in the body, and regulatory T cells make sure everything stays in sync.” Even after a vaccination, T helper cells ensure that the body builds up a specific immune response. This sometimes doesn’t work as well in older people, because among other things the body produces fewer T cells as it gets older.

T cells play a fatal role in organ transplantation

Yet as helpful and indispensable as T cells are for the daily defense against all kinds of pathogens, their role in organ transplantation is fatal. “Here the T cells just go about their work, which involves organizing the defense against the supposedly evil invader,” explains Sawitzki. The immunosuppressants used to prevent transplant rejections suppress the T cells, resulting in the body no longer being able to fight other germs or malignant cells. “Patients often suffer from severe infections or even develop cancer,” says the transplant immunologist, adding that the drugs often also have a toxic effect on transplanted organs: “When patients get a new kidney, the drugs they are given to suppress the immune system damage the organ again.”

Regulatory T cells subdue specific parts of the immune system

To address this issue, Sawitzki and international colleagues came up with the idea of utilizing components of the body’s own immune system. “We knew that regulatory T cells have a dampening effect on the immune defense, but that unlike the drugs they only target the immunologically active defense cells,” she explains. So we thought it might help to increase the number of these T cells in the patient’s body in order to specifically suppress only the rejection of the new organ without simultaneously suppressing all immune responses.” Sawitzki’s research group participated in an international study that examined exactly this question. The researchers took regulatory T cells from donor kidney recipients, multiplied the cells in the laboratory, and put them back into the patients. The scientists led by Sawitzki at the BIH Center for Regenerative Therapies (BCRT) were able to demonstrate that the reintroduced T cells specifically suppressed rejection of the new organ. The clinical trial produced other encouraging results: “The patients needed only very small doses of immunosuppressants, they suffered in comparison much less from infections, and their new kidney worked wonderfully,” Sawitzki recounts.

Professor Christopher Baum, Chair of the BIH Board of Directors and Chief Translational Research Officer of Charité – Universitätsmedizin Berlin, is delighted by the appointment of the new BIH professor: “Regenerative medicine is the medicine of the future. Cell therapies will be used more and more frequently, be it to fight cancer or to advance transplantation medicine and related fields. We are therefore extremely pleased that with Birgit Sawitzki we can expand and consolidate our expertise in this field.”

A bridge builder between disciplines

Sawitzki stresses that immune cells not only communicate with each other during inflammation, but also interact with various organ and vascular cells. “So we need to work closely with colleagues from other disciplines, such as diabetologists, cardiologists, and vascular researchers. I am therefore very much looking forward to the collaboration at the BIH in the Focus Area ‘Translational Vascular Biomedicine.’” During the coronavirus pandemic, the immunologist has been working with colleagues in the fields of infectious diseases and virology to gain a better understanding of the immune response to the SARS-CoV-2 pathogen. And since her research generates such large amounts of data, she will also team up with data scientists at the BIH. “We immunologists are bridge builders between disciplines because the immune system plays a role everywhere.”

Birgit Sawitzki studied biochemistry at the Humboldt-Universität zu Berlin and completed her doctorate at Charité’s Institute of Immunology. A Wellcome Trust fellowship took her to the UK for two years as a postdoc at the University of Oxford. In 2003 she returned to Charité to lead the Transplantation Tolerance Lab at the Institute of Medical Immunology. In 2009 she received a W2 Professorship in Applied Immunology at Charité that focused specifically on transplantation and immune tolerance. With the appointment of Sawitzki, the BIH was able to keep the immunologist from being recruited away for a W3 Professorship and will be able to tap into her expertise for the expansion of the BIH’s translational research activities.

Dr. Stefanie Seltmann

Head of Communications, Press Spokesperson

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