**Abstract**

Pathogen infections are recognized by the immune system, which consists of two types of responses: an innate immune response that recognizes pathogenassociated molecular patterns (PAMPs) and an antigen-specific adaptive immune response. In both responses, there are several activated cells of the immune system, which play a key role in establishing the environment of cytokines, thus directing their differentiation either suppressing or promoting the immune response. This immune response is crucial against pathogen infections. In this chapter, we will describe the crucial role played by different families of cytokines during activation of the immune system to eliminate infectious pathogens.

**Keywords:** cytokines, IL-1, TNF, IL-17, IL-6, IFN, bacteria, fungi, virus, parasites
