First Published in 1988. This is a collection of the Proceedings of a course held at the International School of Medical Sciences Ettore Majorana Centre for Scientific Culture, Italy 5-13 September 1986.

M. Ghione Institute of Microbiology, Milan, Italy. L. Rausa Institute of Pharmacology, Palermo, Italy. A. Pellegrini Institute of General Pathology, Rome, Italy.