Certain cells have been shown to be exquisitely sensitive to cytokines. Consequently, these cells may be modulated - even killed - by neighbouring immunoinflammatory reactions. Since IL-1 is toxic to normal insulin-producing beta-cells, and cellular infiltration of pancreatic islets with IL-1-producing leucocytes precedes the development of insulin-dependent diabetes mellitus (IDDM), IL-1 may be a central pathogenic factor in IDDM.