Innate and adaptive responses are two main branches of the immune system. Communication between cells of these two branches is essential to launching a successful immune response against a foreign antigen. Cytokines play a central role in mediating communication between immune cells. Immune cells include those of the innate system and adaptive system. Innate cells include antigen presenting cells (dendritic cells, macrophages and neutrophils), natural killer (NK) cells, mast cells, basophils and eosinophils. Adaptive immune cells include B cells and T cells. Antigen presenting cells bridge the innate and adaptive branches of the immune system.Cytokines which include interleukins, interferons and TNF play a role in facilitating cross talk between cells of the innate and adaptive systems. Cytokines such as IL-8, IL-1 and IL-10 produced by macrophages lead to the activation of neutrophils, mast cells and basophils. Dendritic cells and macrophages also produce a host of cytokines including IL-1, IL-15, IL-4, TNF and IFN which activate NK cells, T cells and lead to the maturation of dendritic cells.
B and T cells are activated by cytokines such as IL-4, IL-6, IL-10 and IL-12. Differentiation of the T cell population is facilitated by TGF-β (T regulatory cells, Th17), IL-12, IL-23, IL-27 (Th 1), IL-2, IFN-gamma (cytotoxic T cells). Development of B cells is aided by IL-4, IL-5, IL-6 and IL-10 produced by Th2 cells. Thus cytokines are critical for communication between immune cells, sending signals for development, activation and differentiation to cells of the innate and adaptive immune systems.