Dr. Ralf Reinhard Tönjes (RRT; German) is research scientist and group leader at Paul- Ehrlich-Institute (PEI), Federal Institute for Vaccines and Biomedicines, Division of Medical Biotechnology, Langen, Germany. RRT is at PEI since 1991. At current, he is head of section “Non-vital tissue preparations, Xenogeneic cell therapeutics”. As such he is concerned with the fields of human tissue preparations and xenotransplantation. He founded the German working group for xenotransplantation (DAX) in 1998. He teaches as an associate professor (Außerplanmäßiger Professor) for biochemistry at Goethe University, Frankfurt/Main, Germany. RRT’s area of research is focused on endogenous retroviruses and retroelements of men and animals.