Computational modeling of the immune system has enabled the study of the different aspects of the highly complex immune processes. The biology of infection is tremendously complex, including pathogen biology, virulence factors, process of infection, infection patho-physiology, and host response to infection. In the past, experimental approaches were the only path to study such complex processes. Today, with the discovery and application of computational modeling, the understanding of the complex processes in the immune system is promising. In this chapter, we discuss infectious diseases like Helicobactor pylori (H. pylori) and the application of computational modeling in combating them. We a also discuss adaptive immune responses to pathogens in light of computational immunology.