Purity >95% as determined by SDS-PAGE. Interleukin 1 beta (IL-1?) is a pro-inflammatory cytokine that is produced by monocytes, macrophages, and dendritic cells (DCs). IL-1? signals through the IL-1 receptor, type 1 (IL-1R1) to activate the myeloid differentiation primary response 88 (MYD88) signaling pathway, which contains the cytoplasmic Toll/IL-1 receptor (TIR) domain adapter. IL-1? and the independently regulated IL-1? protein have overlapping proinflammatory activities to induce adhesion molecule expression on epithelial cells, control fever induction, initiate rheumatoid arthritis, and promote septic shock.