many different forms and biochemical and biophysical details. However,the final outcome of transmembrane signaling at the cellular level elucidates some cellular functions, which are at the center of se- defense, alimentation, escape reactions, etc. Transmembrane signaling can be studied best in the immune system,in particular in lymphocytes,the main cel- lar carriers of immune defense. The different chapters are independent studies, written by well-known experts in their particular fields. Some chapters include the authors¿ very recent data, generalized, on the one hand, to provide und- standable material for those who are interested in the field but not experts. On the other hand,the current data and novel efforts to unify biochemical and bioph- ical events in a physiological description provide interesting reading for experts as well.