Acknowledgement First of all, I would like to thank Prof. Dr. Burkhart Schraven for giving me the opportunity to work in his institute, providing an international, motivating and enthusiastic atmosphere as well as for his strong scientific guidance. I would like to thank my supervisor Dr. Luca Simeoni for his nearly four years of supervision, and the many useful comments and suggestions I have received over the duration of my work. There are many people to whom I owe a debt of thanks for their support over the last years. I am grateful to my former colleagues Michal Smida, and Dr. Mauro Togni for being nice collaborative colleagues all the time who never refused to share their expertise with me. In addition, they were always nice friends who always put up with my occasional bad mood and helped me to overcome them. I should like to thank Dr. Jonatan Lindquist for being always helpful when I needed it. My special thanks go to Mathias Wolff for his excellent assistance in the animal facility as well as for his patience to deal with my incapability to speak a good German. Needless to say that this dissertation would not exist without the contribution of many supporting people to whom I am also very thankful. Last but certainly not least, I would like to show my gratitude to my wife Anita who gave me continuous emotional support especially during those times when everything went wrong and when I tended to lose my hope and strength to finish my work. Without her support, I would not have been able to complete my thesis.