Cytokines primarily act via paracrine signalling — they are secreted by one cell and act on nearby target cells within the same tissue or organ. However, cytokines can also act in an autocrine manner (acting back on the cell that secreted them — e.g. IL-2 stimulating the T cell that produced it). In systemic inflammation, cytokines can act endocrine (via blood). The primary classification is paracrine for local immune signalling.