Interleukin-1 beta (IL-1 beta), is a 17.5 kDa proinflammatory, cell-associated cytokine, produced by monocytes, tissue macrophages, keratinocytes and other epithelial cells. IL-1 beta promotes the proliferation of memory T cells and cytokine production. It attenuates regulatory T cell function and enables CD4+CD25- autoreactive effectors to avoid suppression. IL-1 beta signals downstream of myc and is required for angiogenesis and invasiveness of tumour cells. IL-1 beta is directly involved in neuronal injury in neurodegenerative disorders, and stimulates mitogenic FGF-like activity, bone resorption and promotes the release of collagenase and prostaglandin from synovial cells.