OpenLB
Open Library of Bioscience

The development of our understanding of the cytokines which began with a collection of barely believable activities in supernatants and extracts from various cell types and has now yielded a well-defined series of molecules with key roles in the control of immunity, infection, differentiation, embryogenesis, and growth is a remarkable and continuing story. Our current, incomplete, understanding of the cytokine network is based on the following observations; 1) Most cytokines are produced by more than one cell type. 2) Different cytokines interact with distinct receptors but can produce markedly overlapping biological effects. Some structurally different cytokines (e.g., IL-1 alpha and IL-1 beta) interact with a single receptor and therefore have identical effects. 3) Most cytokines have multiple biological actions. These actions are dependent on cell type and functional state and are modified by the other mediators to which a cell is simultaneously exposed. 4) A single agent (e.g., lipopolysaccharide or viruses) can induce several different cytokines within the same cell, suggesting the cytokine interaction is important. 5) Cytokines interact within the cytokine network by; (1) stimulating the production of other cytokines; (2) transmodulation of receptors for other cytokines; (3) enhancing or inhibiting the biological activity of other cytokines.