Phagocytic cells and complement are probably the most important components of host defense against bacteria which, after overcoming the mucosal and epithelial barriers, multiply in the subepithelial tissue and may threaten to disseminate and invade the blood stream and different organs. Questions concerning the factors which regulate the interactions of the bacterial cell with host defenses are a challenge to research and lead to practical applications for the prevention, treatment and diagnosis of infectious diseases. The questions of expression and regulation of virulence related bacterial...