For thousands of years, pathogens have fought against the host's immunological responses. Pathogens have developed a range of immune evasion methods to prevent immune recognition of infected cells by inhibiting cytokine activity. To regulate viral and bacterial infection, the immune system has developed a variety of strategies, ranging from direct pathogen killing to the development of cytokines that impede replication. The immune system's response to infectious pathogens, as well as how infectious agents interact with, adapt, or evade the immune system, are studied in infectious disease immunology. Our understanding of the immune response to infection has advanced dramatically in recent years.